diff --git a/contrib/db_pools/codegen/src/database.rs b/contrib/db_pools/codegen/src/database.rs
index 837aa6c8..a2ca218d 100644
--- a/contrib/db_pools/codegen/src/database.rs
+++ b/contrib/db_pools/codegen/src/database.rs
@@ -67,7 +67,7 @@ pub fn derive_database(input: TokenStream) -> TokenStream {
                         ) -> rocket::request::Outcome<Self, Self::Error> {
                             match #db_ty::fetch(req.rocket()) {
                                 Some(db) => rocket::outcome::Outcome::Success(db),
-                                None => rocket::outcome::Outcome::Failure((
+                                None => rocket::outcome::Outcome::Error((
                                     rocket::http::Status::InternalServerError, ()))
                             }
                         }
diff --git a/contrib/db_pools/lib/src/database.rs b/contrib/db_pools/lib/src/database.rs
index 4afbd1f3..b8179be0 100644
--- a/contrib/db_pools/lib/src/database.rs
+++ b/contrib/db_pools/lib/src/database.rs
@@ -164,7 +164,7 @@ pub struct Initializer<D: Database>(Option<&'static str>, PhantomData<fn() -> D>
 /// [`connect_timeout`](crate::Config::connect_timeout) seconds.
 ///   * If the `Initializer` fairing was _not_ attached, the guard _fails_ with
 ///   status `InternalServerError`. A [`Sentinel`] guards this condition, and so
-///   this type of failure is unlikely to occur. A `None` error is returned.
+///   this type of error is unlikely to occur. A `None` error is returned.
 ///   * If a connection is not available within `connect_timeout` seconds or
 ///   another error occurs, the guard _fails_ with status `ServiceUnavailable`
 ///   and the error is returned in `Some`.
@@ -288,9 +288,9 @@ impl<'r, D: Database> FromRequest<'r> for Connection<D> {
         match D::fetch(req.rocket()) {
             Some(db) => match db.get().await {
                 Ok(conn) => Outcome::Success(Connection(conn)),
-                Err(e) => Outcome::Failure((Status::ServiceUnavailable, Some(e))),
+                Err(e) => Outcome::Error((Status::ServiceUnavailable, Some(e))),
             },
-            None => Outcome::Failure((Status::InternalServerError, None)),
+            None => Outcome::Error((Status::InternalServerError, None)),
         }
     }
 }
diff --git a/contrib/dyn_templates/src/metadata.rs b/contrib/dyn_templates/src/metadata.rs
index 06d722d2..9f52f33d 100644
--- a/contrib/dyn_templates/src/metadata.rs
+++ b/contrib/dyn_templates/src/metadata.rs
@@ -153,7 +153,7 @@ impl<'r> FromRequest<'r> for Metadata<'r> {
                 error_!("Uninitialized template context: missing fairing.");
                 info_!("To use templates, you must attach `Template::fairing()`.");
                 info_!("See the `Template` documentation for more information.");
-                request::Outcome::Failure((Status::InternalServerError, ()))
+                request::Outcome::Error((Status::InternalServerError, ()))
             })
     }
 }
diff --git a/contrib/sync_db_pools/lib/src/connection.rs b/contrib/sync_db_pools/lib/src/connection.rs
index a52aae72..c395dc28 100644
--- a/contrib/sync_db_pools/lib/src/connection.rs
+++ b/contrib/sync_db_pools/lib/src/connection.rs
@@ -213,7 +213,7 @@ impl<'r, K: 'static, C: Poolable> FromRequest<'r> for Connection<K, C> {
             Some(c) => c.get().await.into_outcome((Status::ServiceUnavailable, ())),
             None => {
                 error_!("Missing database fairing for `{}`", std::any::type_name::<K>());
-                Outcome::Failure((Status::InternalServerError, ()))
+                Outcome::Error((Status::InternalServerError, ()))
             }
         }
     }
diff --git a/core/codegen/src/attribute/route/mod.rs b/core/codegen/src/attribute/route/mod.rs
index 93fac9b9..e30117db 100644
--- a/core/codegen/src/attribute/route/mod.rs
+++ b/core/codegen/src/attribute/route/mod.rs
@@ -126,9 +126,9 @@ fn request_guard_decl(guard: &Guard) -> TokenStream {
                 #_log::warn_!("Request guard `{}` is forwarding.", stringify!(#ty));
                 return #Outcome::Forward((#__data, __e));
             },
-            #Outcome::Failure((__c, __e)) => {
+            #Outcome::Error((__c, __e)) => {
                 #_log::warn_!("Request guard `{}` failed: {:?}.", stringify!(#ty), __e);
-                return #Outcome::Failure(__c);
+                return #Outcome::Error(__c);
             }
         };
     }
@@ -189,9 +189,9 @@ fn data_guard_decl(guard: &Guard) -> TokenStream {
                 #_log::warn_!("Data guard `{}` is forwarding.", stringify!(#ty));
                 return #Outcome::Forward((__d, __e));
             }
-            #Outcome::Failure((__c, __e)) => {
+            #Outcome::Error((__c, __e)) => {
                 #_log::warn_!("Data guard `{}` failed: {:?}.", stringify!(#ty), __e);
-                return #Outcome::Failure(__c);
+                return #Outcome::Error(__c);
             }
         };
     }
diff --git a/core/codegen/src/lib.rs b/core/codegen/src/lib.rs
index 7cec0eb0..abcf3872 100644
--- a/core/codegen/src/lib.rs
+++ b/core/codegen/src/lib.rs
@@ -239,8 +239,7 @@ macro_rules! route_attribute {
         ///
         ///            If a request guard fails, the request is forwarded if the
         ///            [`Outcome`] is `Forward` or failed if the [`Outcome`] is
-        ///            `Failure`. See [`FromRequest` Outcomes] for further
-        ///            detail.
+        ///            `Error`. See [`FromRequest` Outcomes] for further detail.
         ///
         ///         2. Path and query guards in an unspecified order. If a path
         ///            or query guard fails, the request is forwarded.
@@ -249,7 +248,7 @@ macro_rules! route_attribute {
         ///
         ///            If a data guard fails, the request is forwarded if the
         ///            [`Outcome`] is `Forward` or failed if the [`Outcome`] is
-        ///            `Failure`. See [`FromData`] for further detail.
+        ///            `Error`. See [`FromData`] for further detail.
         ///
         ///      If all validation succeeds, the decorated function is called.
         ///      The returned value is used to generate a [`Response`] via the
@@ -448,7 +447,7 @@ pub fn main(args: TokenStream, input: TokenStream) -> TokenStream {
 /// #[rocket::main]
 /// async fn main() {
 ///     // Recall that an uninspected `Error` will cause a pretty-printed panic,
-///     // so rest assured failures do not go undetected when using `#[launch]`.
+///     // so rest assured errors do not go undetected when using `#[launch]`.
 ///     let _ = rocket().launch().await;
 /// }
 /// ```
diff --git a/core/http/src/parse/uri/tests.rs b/core/http/src/parse/uri/tests.rs
index 7106e4b2..ac7b506c 100644
--- a/core/http/src/parse/uri/tests.rs
+++ b/core/http/src/parse/uri/tests.rs
@@ -8,7 +8,7 @@ macro_rules! assert_parse_eq {
             match from_str($from) {
                 Ok(output) => {
                     if output != expected {
-                        println!("Failure on: {:?}", $from);
+                        println!("Error on: {:?}", $from);
                         assert_eq!(output, expected, "{} != {}", output, expected);
                     }
                 }
@@ -53,7 +53,7 @@ macro_rules! assert_displays_eq {
                 Ok(output) => {
                     let output_string = output.to_string();
                     if output_string != string {
-                        println!("Failure on: {:?}", $string);
+                        println!("Error on: {:?}", $string);
                         println!("Got: {:?}", output_string);
                         println!("Parsed as: {:?}", output);
                         panic!("failed");
diff --git a/core/http/src/tls/mtls.rs b/core/http/src/tls/mtls.rs
index 9d7554fb..45ea38fc 100644
--- a/core/http/src/tls/mtls.rs
+++ b/core/http/src/tls/mtls.rs
@@ -533,7 +533,7 @@ impl fmt::Display for Name<'_> {
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            Error::Parse(e) => write!(f, "parse failure: {}", e),
+            Error::Parse(e) => write!(f, "parse error: {}", e),
             Error::Incomplete(_) => write!(f, "incomplete certificate data"),
             Error::Trailing(n) => write!(f, "found {} trailing bytes", n),
             Error::Empty => write!(f, "empty certificate chain"),
diff --git a/core/lib/src/catcher/catcher.rs b/core/lib/src/catcher/catcher.rs
index 3ed8ff32..299d7b08 100644
--- a/core/lib/src/catcher/catcher.rs
+++ b/core/lib/src/catcher/catcher.rs
@@ -18,12 +18,14 @@ use yansi::Paint;
 ///
 ///   * A failing guard.
 ///   * A failing responder.
+///   * A forwarding guard.
 ///   * Routing failure.
 ///
-/// Each failure is paired with a status code. Guards and responders indicate
-/// the status code themselves via their `Err` return value while a routing
-/// failure is always a `404`. Rocket invokes the error handler for the catcher
-/// with the error's status code.
+/// Each error or forward is paired with a status code. Guards and responders
+/// indicate the status code themselves via their `Err` and `Outcome` return
+/// value. A complete routing failure is always a `404`. Rocket invokes the
+/// error handler for the catcher with an error's status code, or in the case of
+/// every route resulting in a forward, the last forwarded status code.
 ///
 /// ### Error Handler Restrictions
 ///
@@ -33,7 +35,7 @@ use yansi::Paint;
 ///
 /// # Routing
 ///
-/// If a route fails by returning a failure [`Outcome`], Rocket routes the
+/// If a route fails by returning an error [`Outcome`], Rocket routes the
 /// erroring request to the highest precedence catcher among all the catchers
 /// that [match](Catcher::matches()). See [`Catcher::matches()`] for details on
 /// matching. Precedence is determined by the catcher's _base_, which is
diff --git a/core/lib/src/config/config.rs b/core/lib/src/config/config.rs
index 61b25bff..4a23bf4f 100644
--- a/core/lib/src/config/config.rs
+++ b/core/lib/src/config/config.rs
@@ -288,7 +288,7 @@ impl Config {
     ///
     /// # Panics
     ///
-    /// If extraction fails, prints an error message indicating the failure and
+    /// If extraction fails, prints an error message indicating the error and
     /// panics. For a version that doesn't panic, use [`Config::try_from()`].
     ///
     /// # Example
diff --git a/core/lib/src/config/secret_key.rs b/core/lib/src/config/secret_key.rs
index 445f9601..02947e70 100644
--- a/core/lib/src/config/secret_key.rs
+++ b/core/lib/src/config/secret_key.rs
@@ -52,7 +52,7 @@ enum Kind {
 /// ```
 ///
 /// When running in any other profile with the `secrets` feature enabled,
-/// providing a key of `0` or not provided a key at all results in a failure at
+/// providing a key of `0` or not provided a key at all results in an error at
 /// launch-time:
 ///
 /// ```rust
@@ -67,7 +67,7 @@ enum Kind {
 ///     .select(profile.clone());
 ///
 /// let rocket = rocket::custom(figment);
-/// let error = Client::tracked(rocket).expect_err("failure in non-debug");
+/// let error = Client::tracked(rocket).expect_err("error in non-debug");
 /// assert!(matches!(error.kind(), ErrorKind::InsecureSecretKey(profile)));
 /// ```
 ///
diff --git a/core/lib/src/data/capped.rs b/core/lib/src/data/capped.rs
index 335c980f..804a42d4 100644
--- a/core/lib/src/data/capped.rs
+++ b/core/lib/src/data/capped.rs
@@ -260,10 +260,10 @@ macro_rules! impl_strict_from_data_from_capped {
                     Success(p) if p.is_complete() => Success(p.into_inner()),
                     Success(_) => {
                         let e = Error::new(UnexpectedEof, "data limit exceeded");
-                        Failure((Status::BadRequest, e.into()))
+                        Error((Status::BadRequest, e.into()))
                     },
                     Forward(d) => Forward(d),
-                    Failure((s, e)) => Failure((s, e)),
+                    Error((s, e)) => Error((s, e)),
                 }
             }
         }
diff --git a/core/lib/src/data/from_data.rs b/core/lib/src/data/from_data.rs
index 2b7465c3..b3ac98c8 100644
--- a/core/lib/src/data/from_data.rs
+++ b/core/lib/src/data/from_data.rs
@@ -10,14 +10,14 @@ pub type Outcome<'r, T, E = <T as FromData<'r>>::Error>
     = outcome::Outcome<T, (Status, E), (Data<'r>, Status)>;
 
 impl<'r, S, E> IntoOutcome<S, (Status, E), (Data<'r>, Status)> for Result<S, E> {
-    type Failure = Status;
+    type Error = Status;
     type Forward = (Data<'r>, Status);
 
     #[inline]
     fn into_outcome(self, status: Status) -> Outcome<'r, S, E> {
         match self {
             Ok(val) => Success(val),
-            Err(err) => Failure((status, err))
+            Err(err) => Error((status, err))
         }
     }
 
@@ -251,6 +251,7 @@ impl<'r, S, E> IntoOutcome<S, (Status, E), (Data<'r>, Status)> for Result<S, E>
 /// use rocket::request::{self, Request};
 /// use rocket::data::{self, Data, FromData, ToByteUnit};
 /// use rocket::http::{Status, ContentType};
+/// use rocket::outcome::Outcome;
 ///
 /// #[derive(Debug)]
 /// enum Error {
@@ -266,12 +267,11 @@ impl<'r, S, E> IntoOutcome<S, (Status, E), (Data<'r>, Status)> for Result<S, E>
 ///
 ///     async fn from_data(req: &'r Request<'_>, data: Data<'r>) -> data::Outcome<'r, Self> {
 ///         use Error::*;
-///         use rocket::outcome::Outcome::*;
 ///
 ///         // Ensure the content type is correct before opening the data.
 ///         let person_ct = ContentType::new("application", "x-person");
 ///         if req.content_type() != Some(&person_ct) {
-///             return Forward((data, Status::NotFound));
+///             return Outcome::Forward((data, Status::NotFound));
 ///         }
 ///
 ///         // Use a configured limit with name 'person' or fallback to default.
@@ -280,8 +280,8 @@ impl<'r, S, E> IntoOutcome<S, (Status, E), (Data<'r>, Status)> for Result<S, E>
 ///         // Read the data into a string.
 ///         let string = match data.open(limit).into_string().await {
 ///             Ok(string) if string.is_complete() => string.into_inner(),
-///             Ok(_) => return Failure((Status::PayloadTooLarge, TooLarge)),
-///             Err(e) => return Failure((Status::InternalServerError, Io(e))),
+///             Ok(_) => return Outcome::Error((Status::PayloadTooLarge, TooLarge)),
+///             Err(e) => return Outcome::Error((Status::InternalServerError, Io(e))),
 ///         };
 ///
 ///         // We store `string` in request-local cache for long-lived borrows.
@@ -290,16 +290,16 @@ impl<'r, S, E> IntoOutcome<S, (Status, E), (Data<'r>, Status)> for Result<S, E>
 ///         // Split the string into two pieces at ':'.
 ///         let (name, age) = match string.find(':') {
 ///             Some(i) => (&string[..i], &string[(i + 1)..]),
-///             None => return Failure((Status::UnprocessableEntity, NoColon)),
+///             None => return Outcome::Error((Status::UnprocessableEntity, NoColon)),
 ///         };
 ///
 ///         // Parse the age.
 ///         let age: u16 = match age.parse() {
 ///             Ok(age) => age,
-///             Err(_) => return Failure((Status::UnprocessableEntity, InvalidAge)),
+///             Err(_) => return Outcome::Error((Status::UnprocessableEntity, InvalidAge)),
 ///         };
 ///
-///         Success(Person { name, age })
+///         Outcome::Success(Person { name, age })
 ///     }
 /// }
 ///
@@ -331,7 +331,7 @@ pub trait FromData<'r>: Sized {
     ///
     /// If validation and parsing succeeds, an outcome of `Success` is returned.
     /// If the data is not appropriate given the type of `Self`, `Forward` is
-    /// returned. If parsing fails, `Failure` is returned.
+    /// returned. If parsing fails, `Error` is returned.
     async fn from_data(req: &'r Request<'_>, data: Data<'r>) -> Outcome<'r, Self>;
 }
 
@@ -428,7 +428,7 @@ impl<'r, T: FromData<'r> + 'r> FromData<'r> for Result<T, T::Error> {
     async fn from_data(req: &'r Request<'_>, data: Data<'r>) -> Outcome<'r, Self> {
         match T::from_data(req, data).await {
             Success(v) => Success(Ok(v)),
-            Failure((_, e)) => Success(Err(e)),
+            Error((_, e)) => Success(Err(e)),
             Forward(d) => Forward(d),
         }
     }
@@ -441,7 +441,7 @@ impl<'r, T: FromData<'r>> FromData<'r> for Option<T> {
     async fn from_data(req: &'r Request<'_>, data: Data<'r>) -> Outcome<'r, Self> {
         match T::from_data(req, data).await {
             Success(v) => Success(Some(v)),
-            Failure(..) | Forward(..) => Success(None),
+            Error(..) | Forward(..) => Success(None),
         }
     }
 }
diff --git a/core/lib/src/error.rs b/core/lib/src/error.rs
index b68b255b..28e71fc2 100644
--- a/core/lib/src/error.rs
+++ b/core/lib/src/error.rs
@@ -216,9 +216,9 @@ impl Error {
                 crate::config::pretty_print_error(error.clone());
                 "aborting due to invalid configuration"
             }
-            ErrorKind::SentinelAborts(ref failures) => {
+            ErrorKind::SentinelAborts(ref errors) => {
                 error!("Rocket failed to launch due to aborting sentinels:");
-                for sentry in failures {
+                for sentry in errors {
                     let name = sentry.type_name.primary().bold();
                     let (file, line, col) = sentry.location;
                     info_!("{} ({}:{}:{})", name, file, line, col);
diff --git a/core/lib/src/fairing/mod.rs b/core/lib/src/fairing/mod.rs
index 642b80b8..1439d8f4 100644
--- a/core/lib/src/fairing/mod.rs
+++ b/core/lib/src/fairing/mod.rs
@@ -66,7 +66,7 @@ pub type Result<T = Rocket<Build>, E = Rocket<Build>> = std::result::Result<T, E
 
 // We might imagine that a request fairing returns an `Outcome`. If it returns
 // `Success`, we don't do any routing and use that response directly. Same if it
-// returns `Failure`. We only route if it returns `Forward`. I've chosen not to
+// returns `Error`. We only route if it returns `Forward`. I've chosen not to
 // go this direction because I feel like request guards are the correct
 // mechanism to use here. In other words, enabling this at the fairing level
 // encourages implicit handling, a bad practice. Fairings can still, however,
@@ -125,7 +125,7 @@ pub type Result<T = Rocket<Build>, E = Rocket<Build>> = std::result::Result<T, E
 ///     recursively attaching ignite fairings. It returns `Ok` if it would like
 ///     ignition and launch to proceed nominally and `Err` otherwise. If an
 ///     ignite fairing returns `Err`, launch will be aborted. All ignite
-///     fairings are executed even if one or more signal a failure.
+///     fairings are executed even if one or more signal an error.
 ///
 ///   * **<a name="liftoff">Liftoff</a> (`on_liftoff`)**
 ///
@@ -417,7 +417,7 @@ pub type Result<T = Rocket<Build>, E = Rocket<Build>> = std::result::Result<T, E
 ///     async fn from_request(request: &'r Request<'_>) -> request::Outcome<Self, ()> {
 ///         match *request.local_cache(|| TimerStart(None)) {
 ///             TimerStart(Some(time)) => request::Outcome::Success(StartTime(time)),
-///             TimerStart(None) => request::Outcome::Failure((Status::InternalServerError, ())),
+///             TimerStart(None) => request::Outcome::Error((Status::InternalServerError, ())),
 ///         }
 ///     }
 /// }
diff --git a/core/lib/src/form/error.rs b/core/lib/src/form/error.rs
index 7167eb5e..b6f3c506 100644
--- a/core/lib/src/form/error.rs
+++ b/core/lib/src/form/error.rs
@@ -350,7 +350,7 @@ impl<'v> Errors<'v> {
     /// Returns the highest [`Error::status()`] of all of the errors in `self`
     /// or [`Status::InternalServerError`] if `self` is empty. This is the
     /// status that is set by the [`Form`](crate::form::Form) data guard on
-    /// failure.
+    /// error.
     ///
     /// See [`Error::status()`] for the corresponding status code of each
     /// [`Error`] variant.
diff --git a/core/lib/src/form/form.rs b/core/lib/src/form/form.rs
index c747adc2..12b1c40c 100644
--- a/core/lib/src/form/form.rs
+++ b/core/lib/src/form/form.rs
@@ -65,8 +65,8 @@ use crate::form::prelude::*;
 ///
 /// If the request `ContentType` _does_ identify as a form but the form data
 /// does not parse as `T`, according to `T`'s [`FromForm`] implementation, the
-/// guard **fails**. The `Failure` variant contains of the [`Errors`] emitted by
-/// `T`'s `FromForm` parser. If the error is not caught by a
+/// guard **fails**. The `Error` variant contains a vector of the [`Errors`]
+/// emitted by `T`'s `FromForm` parser. If the error is not caught by a
 /// [`form::Result<T>`](Result) or `Option<Form<T>>` data guard, the status code
 /// is set to [`Errors::status()`], and the corresponding error catcher is
 /// called.
@@ -334,7 +334,7 @@ impl<'r, T: FromForm<'r>> FromData<'r> for Form<T> {
 
         match T::finalize(context) {
             Ok(value) => Outcome::Success(Form(value)),
-            Err(e) => Outcome::Failure((e.status(), e)),
+            Err(e) => Outcome::Error((e.status(), e)),
         }
     }
 }
diff --git a/core/lib/src/form/from_form_field.rs b/core/lib/src/form/from_form_field.rs
index d03ee386..7e733133 100644
--- a/core/lib/src/form/from_form_field.rs
+++ b/core/lib/src/form/from_form_field.rs
@@ -297,7 +297,7 @@ impl<'v> FromFormField<'v> for Capped<&'v str> {
 
         match <Capped<&'v str> as FromData>::from_data(f.request, f.data).await {
             Outcome::Success(p) => Ok(p),
-            Outcome::Failure((_, e)) => Err(e)?,
+            Outcome::Error((_, e)) => Err(e)?,
             Outcome::Forward(..) => {
                 Err(Error::from(ErrorKind::Unexpected).with_entity(Entity::DataField))?
             }
@@ -318,7 +318,7 @@ impl<'v> FromFormField<'v> for Capped<String> {
 
         match <Capped<String> as FromData>::from_data(f.request, f.data).await {
             Outcome::Success(p) => Ok(p),
-            Outcome::Failure((_, e)) => Err(e)?,
+            Outcome::Error((_, e)) => Err(e)?,
             Outcome::Forward(..) => {
                 Err(Error::from(ErrorKind::Unexpected).with_entity(Entity::DataField))?
             }
@@ -354,7 +354,7 @@ impl<'v> FromFormField<'v> for Capped<&'v [u8]> {
 
         match <Capped<&'v [u8]> as FromData>::from_data(f.request, f.data).await {
             Outcome::Success(p) => Ok(p),
-            Outcome::Failure((_, e)) => Err(e)?,
+            Outcome::Error((_, e)) => Err(e)?,
             Outcome::Forward(..) => {
                 Err(Error::from(ErrorKind::Unexpected).with_entity(Entity::DataField))?
             }
diff --git a/core/lib/src/form/parser.rs b/core/lib/src/form/parser.rs
index 89c42eb8..7a9c4437 100644
--- a/core/lib/src/form/parser.rs
+++ b/core/lib/src/form/parser.rs
@@ -40,7 +40,7 @@ impl<'r, 'i> Parser<'r, 'i> {
 
         match parser {
             Ok(storage) => Outcome::Success(storage),
-            Err(e) => Outcome::Failure((e.status(), e.into()))
+            Err(e) => Outcome::Error((e.status(), e.into()))
         }
     }
 
diff --git a/core/lib/src/form/validate.rs b/core/lib/src/form/validate.rs
index 821589cb..6a079be0 100644
--- a/core/lib/src/form/validate.rs
+++ b/core/lib/src/form/validate.rs
@@ -159,7 +159,7 @@ crate::export! {
 
 /// Equality validator: succeeds exactly when `a` == `b`, using [`PartialEq`].
 ///
-/// On failure, returns a validation error with the following message:
+/// On error, returns a validation error with the following message:
 ///
 /// ```text
 /// value does not match expected value
@@ -236,7 +236,7 @@ pub fn dbg_eq<'v, A, B>(a: &A, b: B) -> Result<'v, ()>
 /// Negative equality validator: succeeds exactly when `a` != `b`, using
 /// [`PartialEq`].
 ///
-/// On failure, returns a validation error with the following message:
+/// On error, returns a validation error with the following message:
 ///
 /// ```text
 /// value is equal to an invalid value
@@ -361,7 +361,7 @@ impl<L, T: Len<L>> Len<L> for crate::serde::msgpack::MsgPack<T> {
 
 /// Length validator: succeeds when the length of a value is within a `range`.
 ///
-/// The value must implement [`Len`]. On failure, returns an [`InvalidLength`]
+/// The value must implement [`Len`]. On error, returns an [`InvalidLength`]
 /// error. See [`Len`] for supported types and how their length is computed.
 ///
 /// [`InvalidLength`]: crate::form::error::ErrorKind::InvalidLength
@@ -504,7 +504,7 @@ impl<I, T: Contains<I> + ?Sized> Contains<I> for &T {
 /// [`Contains<I>`](Contains) where `I` is the type of the `item`. See
 /// [`Contains`] for supported types and items.
 ///
-/// On failure, returns a validation error with the following message:
+/// On error, returns a validation error with the following message:
 ///
 /// ```text
 /// value is equal to an invalid value
@@ -590,7 +590,7 @@ pub fn dbg_contains<'v, V, I>(value: V, item: I) -> Result<'v, ()>
 /// [`Contains<I>`](Contains) where `I` is the type of the `item`. See
 /// [`Contains`] for supported types and items.
 ///
-/// On failure, returns a validation error with the following message:
+/// On error, returns a validation error with the following message:
 ///
 /// ```text
 /// value contains a disallowed item
@@ -670,7 +670,7 @@ pub fn dbg_omits<'v, V, I>(value: V, item: I) -> Result<'v, ()>
 /// Integer range validator: succeeds when an integer value is within a range.
 ///
 /// The value must be an integer type that implement `TryInto<isize> + Copy`. On
-/// failure, returns an [`OutOfRange`] error.
+/// error, returns an [`OutOfRange`] error.
 ///
 /// [`OutOfRange`]: crate::form::error::ErrorKind::OutOfRange
 ///
@@ -719,7 +719,7 @@ pub fn range<'v, V, R>(value: &V, range: R) -> Result<'v, ()>
 /// the `item`. The iterator must be [`Clone`]. See [`Contains`] for supported
 /// types and items. The item must be [`Debug`].
 ///
-/// On failure, returns a [`InvalidChoice`] error with the debug representation
+/// On error, returns a [`InvalidChoice`] error with the debug representation
 /// of each item in `items`.
 ///
 /// [`InvalidChoice`]: crate::form::error::ErrorKind::InvalidChoice
@@ -762,7 +762,7 @@ pub fn one_of<'v, V, I, R>(value: V, items: R) -> Result<'v, ()>
 /// File type validator: succeeds when a [`TempFile`] has the Content-Type
 /// `content_type`.
 ///
-/// On failure, returns a validation error with one of the following messages:
+/// On error, returns a validation error with one of the following messages:
 ///
 /// ```text
 /// // the file has an incorrect extension
@@ -810,7 +810,7 @@ pub fn ext<'v>(file: &TempFile<'_>, r#type: ContentType) -> Result<'v, ()> {
 /// when a more case-specific option does not exist. It succeeds exactly when
 /// `f` returns `true` and fails otherwise.
 ///
-/// On failure, returns a validation error with the message `msg`.
+/// On error, returns a validation error with the message `msg`.
 ///
 /// # Example
 ///
@@ -860,7 +860,7 @@ pub fn with<'v, V, F, M>(value: V, f: F, msg: M) -> Result<'v, ()>
 /// Along with [`with`], this is the most generic validator. It succeeds
 /// exactly when `f` returns `Ok` and fails otherwise.
 ///
-/// On failure, returns a validation error with the message in the `Err`
+/// On error, returns a validation error with the message in the `Err`
 /// variant converted into a string.
 ///
 /// # Example
diff --git a/core/lib/src/fs/server.rs b/core/lib/src/fs/server.rs
index da78ec33..8aac5c25 100644
--- a/core/lib/src/fs/server.rs
+++ b/core/lib/src/fs/server.rs
@@ -148,12 +148,12 @@ impl FileServer {
             if !options.contains(Options::IndexFile) && !path.is_dir() {
                 let path = path.display();
                 error!("FileServer path '{}' is not a directory.", path.primary());
-                warn_!("Aborting early to prevent inevitable handler failure.");
+                warn_!("Aborting early to prevent inevitable handler error.");
                 panic!("invalid directory: refusing to continue");
             } else if !path.exists() {
                 let path = path.display();
                 error!("FileServer path '{}' is not a file.", path.primary());
-                warn_!("Aborting early to prevent inevitable handler failure.");
+                warn_!("Aborting early to prevent inevitable handler error.");
                 panic!("invalid file: refusing to continue");
             }
         }
diff --git a/core/lib/src/outcome.rs b/core/lib/src/outcome.rs
index 44a38f89..549e8509 100644
--- a/core/lib/src/outcome.rs
+++ b/core/lib/src/outcome.rs
@@ -1,10 +1,10 @@
-//! Success, failure, and forward handling.
+//! Success, error, and forward handling.
 //!
 //! The `Outcome<S, E, F>` type is similar to the standard library's `Result<S,
 //! E>` type. It is an enum with three variants, each containing a value:
-//! `Success(S)`, which represents a successful outcome, `Failure(E)`, which
-//! represents a failing outcome, and `Forward(F)`, which represents neither a
-//! success or failure, but instead, indicates that processing could not be
+//! `Success(S)`, which represents a successful outcome, `Error(E)`, which
+//! represents an erroring outcome, and `Forward(F)`, which represents neither a
+//! success or error, but instead, indicates that processing could not be
 //! handled and should instead be _forwarded_ to whatever can handle the
 //! processing next.
 //!
@@ -35,15 +35,15 @@
 //! `Success(S)`. If `from_data` returns a `Success`, the `Success` value will
 //! be unwrapped and the value will be used as the value of `my_val`.
 //!
-//! # Failure
+//! # Error
 //!
-//! A failure `Outcome<S, E, F>`, `Failure(E)`, is returned when a function
+//! An error `Outcome<S, E, F>`, `Error(E)`, is returned when a function
 //! fails with some error and no processing can or should continue as a result.
-//! The meaning of a failure depends on the context.
+//! The meaning of an error depends on the context.
 //!
-//! In Rocket, a `Failure` generally means that a request is taken out of normal
+//! In Rocket, an `Error` generally means that a request is taken out of normal
 //! processing. The request is then given to the catcher corresponding to some
-//! status code. Users can catch failures by requesting a type of `Result<S, E>`
+//! status code. Users can catch errors by requesting a type of `Result<S, E>`
 //! or `Option<S>` in request handlers. For example, if a user's handler looks
 //! like:
 //!
@@ -56,10 +56,9 @@
 //! ```
 //!
 //! The [`FromData`] implementation for the type `S` returns an `Outcome` with a
-//! `Success(S)` and `Failure(E)`. If `from_data` returns a `Failure`, the
-//! `Failure` value will be unwrapped and the value will be used as the `Err`
-//! value of `my_val` while a `Success` will be unwrapped and used the `Ok`
-//! value.
+//! `Success(S)` and `Error(E)`. If `from_data` returns an `Error`, the `Error`
+//! value will be unwrapped and the value will be used as the `Err` value of
+//! `my_val` while a `Success` will be unwrapped and used the `Ok` value.
 //!
 //! # Forward
 //!
@@ -79,11 +78,11 @@
 //! ```
 //!
 //! The [`FromData`] implementation for the type `S` returns an `Outcome` with a
-//! `Success(S)`, `Failure(E)`, and `Forward(F)`. If the `Outcome` is a
+//! `Success(S)`, `Error(E)`, and `Forward(F)`. If the `Outcome` is a
 //! `Forward`, the `hello` handler isn't called. Instead, the incoming request
 //! is forwarded, or passed on to, the next matching route, if any. Ultimately,
 //! if there are no non-forwarding routes, forwarded requests are handled by the
-//! 404 catcher. Similar to `Failure`s, users can catch `Forward`s by requesting
+//! 404 catcher. Similar to `Error`s, users can catch `Forward`s by requesting
 //! a type of `Option<S>`. If an `Outcome` is a `Forward`, the `Option` will be
 //! `None`.
 
@@ -93,8 +92,8 @@ use yansi::{Paint, Color};
 
 use self::Outcome::*;
 
-/// An enum representing success (`Success`), failure (`Failure`), or
-/// forwarding (`Forward`).
+/// An enum representing success (`Success`), error (`Error`), or forwarding
+/// (`Forward`).
 ///
 /// See the [top level documentation](crate::outcome) for detailed information.
 #[must_use]
@@ -102,24 +101,24 @@ use self::Outcome::*;
 pub enum Outcome<S, E, F> {
     /// Contains the success value.
     Success(S),
-    /// Contains the failure error value.
-    Failure(E),
+    /// Contains the error error value.
+    Error(E),
     /// Contains the value to forward on.
     Forward(F),
 }
 
 /// Conversion trait from some type into an Outcome type.
 pub trait IntoOutcome<S, E, F> {
-    /// The type to use when returning an `Outcome::Failure`.
-    type Failure: Sized;
+    /// The type to use when returning an `Outcome::Error`.
+    type Error: Sized;
 
     /// The type to use when returning an `Outcome::Forward`.
     type Forward: Sized;
 
     /// Converts `self` into an `Outcome`. If `self` represents a success, an
-    /// `Outcome::Success` is returned. Otherwise, an `Outcome::Failure` is
-    /// returned with `failure` as the inner value.
-    fn into_outcome(self, failure: Self::Failure) -> Outcome<S, E, F>;
+    /// `Outcome::Success` is returned. Otherwise, an `Outcome::Error` is
+    /// returned with `error` as the inner value.
+    fn into_outcome(self, error: Self::Error) -> Outcome<S, E, F>;
 
     /// Converts `self` into an `Outcome`. If `self` represents a success, an
     /// `Outcome::Success` is returned. Otherwise, an `Outcome::Forward` is
@@ -128,14 +127,14 @@ pub trait IntoOutcome<S, E, F> {
 }
 
 impl<S, E, F> IntoOutcome<S, E, F> for Option<S> {
-    type Failure = E;
+    type Error = E;
     type Forward = F;
 
     #[inline]
-    fn into_outcome(self, failure: E) -> Outcome<S, E, F> {
+    fn into_outcome(self, error: E) -> Outcome<S, E, F> {
         match self {
             Some(val) => Success(val),
-            None => Failure(failure)
+            None => Error(error)
         }
     }
 
@@ -208,7 +207,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let x: Outcome<i32, &str, usize> = Success(10);
     /// assert_eq!(x.is_success(), true);
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
+    /// let x: Outcome<i32, &str, usize> = Error("Hi! I'm an error.");
     /// assert_eq!(x.is_success(), false);
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(25);
@@ -219,7 +218,7 @@ impl<S, E, F> Outcome<S, E, F> {
         matches!(self, Success(_))
     }
 
-    /// Return true if this `Outcome` is a `Failure`.
+    /// Return true if this `Outcome` is an `Error`.
     ///
     /// # Examples
     ///
@@ -228,17 +227,17 @@ impl<S, E, F> Outcome<S, E, F> {
     /// # use rocket::outcome::Outcome::*;
     /// #
     /// let x: Outcome<i32, &str, usize> = Success(10);
-    /// assert_eq!(x.is_failure(), false);
+    /// assert_eq!(x.is_error(), false);
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
-    /// assert_eq!(x.is_failure(), true);
+    /// let x: Outcome<i32, &str, usize> = Error("Hi! I'm an error.");
+    /// assert_eq!(x.is_error(), true);
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(25);
-    /// assert_eq!(x.is_failure(), false);
+    /// assert_eq!(x.is_error(), false);
     /// ```
     #[inline]
-    pub fn is_failure(&self) -> bool {
-        matches!(self, Failure(_))
+    pub fn is_error(&self) -> bool {
+        matches!(self, Error(_))
     }
 
     /// Return true if this `Outcome` is a `Forward`.
@@ -252,7 +251,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let x: Outcome<i32, &str, usize> = Success(10);
     /// assert_eq!(x.is_forward(), false);
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
+    /// let x: Outcome<i32, &str, usize> = Error("Hi! I'm an error.");
     /// assert_eq!(x.is_forward(), false);
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(25);
@@ -275,7 +274,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let x: Outcome<i32, &str, usize> = Success(10);
     /// assert_eq!(x.succeeded(), Some(10));
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
+    /// let x: Outcome<i32, &str, usize> = Error("Hi! I'm an error.");
     /// assert_eq!(x.succeeded(), None);
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(25);
@@ -291,7 +290,7 @@ impl<S, E, F> Outcome<S, E, F> {
 
     /// Converts from `Outcome<S, E, F>` to `Option<E>`.
     ///
-    /// Returns the `Some` of the `Failure` if this is a `Failure`, otherwise
+    /// Returns the `Some` of the `Error` if this is an `Error`, otherwise
     /// returns `None`. `self` is consumed, and all other values are discarded.
     ///
     /// ```rust
@@ -301,7 +300,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let x: Outcome<i32, &str, usize> = Success(10);
     /// assert_eq!(x.failed(), None);
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
+    /// let x: Outcome<i32, &str, usize> = Error("Hi! I'm an error.");
     /// assert_eq!(x.failed(), Some("Hi! I'm an error."));
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(25);
@@ -310,7 +309,7 @@ impl<S, E, F> Outcome<S, E, F> {
     #[inline]
     pub fn failed(self) -> Option<E> {
         match self {
-            Failure(val) => Some(val),
+            Error(val) => Some(val),
             _ => None
         }
     }
@@ -327,7 +326,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let x: Outcome<i32, &str, usize> = Success(10);
     /// assert_eq!(x.forwarded(), None);
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
+    /// let x: Outcome<i32, &str, usize> = Error("Hi! I'm an error.");
     /// assert_eq!(x.forwarded(), None);
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(25);
@@ -355,7 +354,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let x: Outcome<i32, &str, usize> = Success(10);
     /// assert_eq!(x.success_or(false), Ok(10));
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
+    /// let x: Outcome<i32, &str, usize> = Error("Hi! I'm an error.");
     /// assert_eq!(x.success_or(false), Err(false));
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(25);
@@ -384,7 +383,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let x: Outcome<i32, &str, usize> = Success(10);
     /// assert_eq!(x.success_or_else(|| false), Ok(10));
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
+    /// let x: Outcome<i32, &str, usize> = Error("Hi! I'm an error.");
     /// assert_eq!(x.success_or_else(|| false), Err(false));
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(25);
@@ -407,14 +406,14 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let x: Outcome<i32, &str, usize> = Success(10);
     /// assert_eq!(x.as_ref(), Success(&10));
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
-    /// assert_eq!(x.as_ref(), Failure(&"Hi! I'm an error."));
+    /// let x: Outcome<i32, &str, usize> = Error("Hi! I'm an error.");
+    /// assert_eq!(x.as_ref(), Error(&"Hi! I'm an error."));
     /// ```
     #[inline]
     pub fn as_ref(&self) -> Outcome<&S, &E, &F> {
         match *self {
             Success(ref val) => Success(val),
-            Failure(ref val) => Failure(val),
+            Error(ref val) => Error(val),
             Forward(ref val) => Forward(val),
         }
     }
@@ -436,7 +435,7 @@ impl<S, E, F> Outcome<S, E, F> {
     pub fn as_mut(&mut self) -> Outcome<&mut S, &mut E, &mut F> {
         match *self {
             Success(ref mut val) => Success(val),
-            Failure(ref mut val) => Failure(val),
+            Error(ref mut val) => Error(val),
             Forward(ref mut val) => Forward(val),
         }
     }
@@ -458,29 +457,29 @@ impl<S, E, F> Outcome<S, E, F> {
     pub fn map<T, M: FnOnce(S) -> T>(self, f: M) -> Outcome<T, E, F> {
         match self {
             Success(val) => Success(f(val)),
-            Failure(val) => Failure(val),
+            Error(val) => Error(val),
             Forward(val) => Forward(val),
         }
     }
 
-    /// Maps the `Failure` value using `f`. Maps an `Outcome<S, E, F>` to an
+    /// Maps the `Error` value using `f`. Maps an `Outcome<S, E, F>` to an
     /// `Outcome<S, T, F>` by applying the function `f` to the value of type `E`
-    /// in `self` if `self` is an `Outcome::Failure`.
+    /// in `self` if `self` is an `Outcome::Error`.
     ///
     /// ```rust
     /// # use rocket::outcome::Outcome;
     /// # use rocket::outcome::Outcome::*;
     /// #
-    /// let x: Outcome<i32, &str, usize> = Failure("hi");
+    /// let x: Outcome<i32, &str, usize> = Error("hi");
     ///
-    /// let mapped = x.map_failure(|v| if v == "hi" { 10 } else { 0 });
-    /// assert_eq!(mapped, Failure(10));
+    /// let mapped = x.map_error(|v| if v == "hi" { 10 } else { 0 });
+    /// assert_eq!(mapped, Error(10));
     /// ```
     #[inline]
-    pub fn map_failure<T, M: FnOnce(E) -> T>(self, f: M) -> Outcome<S, T, F> {
+    pub fn map_error<T, M: FnOnce(E) -> T>(self, f: M) -> Outcome<S, T, F> {
         match self {
             Success(val) => Success(val),
-            Failure(val) => Failure(f(val)),
+            Error(val) => Error(f(val)),
             Forward(val) => Forward(val),
         }
     }
@@ -502,7 +501,7 @@ impl<S, E, F> Outcome<S, E, F> {
     pub fn map_forward<T, M: FnOnce(F) -> T>(self, f: M) -> Outcome<S, E, T> {
         match self {
             Success(val) => Success(val),
-            Failure(val) => Failure(val),
+            Error(val) => Error(val),
             Forward(val) => Forward(f(val)),
         }
     }
@@ -523,7 +522,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let mapped = x.and_then(|v| match v {
     ///    10 => Success("10"),
     ///    1 => Forward(false),
-    ///    _ => Failure("30")
+    ///    _ => Error("30")
     /// });
     ///
     /// assert_eq!(mapped, Success("10"));
@@ -532,15 +531,15 @@ impl<S, E, F> Outcome<S, E, F> {
     pub fn and_then<T, M: FnOnce(S) -> Outcome<T, E, F>>(self, f: M) -> Outcome<T, E, F> {
         match self {
             Success(val) => f(val),
-            Failure(val) => Failure(val),
+            Error(val) => Error(val),
             Forward(val) => Forward(val),
         }
     }
 
     /// Converts from `Outcome<S, E, F>` to `Outcome<S, T, F>` using `f` to map
-    /// `Failure(E)` to `Failure(T)`.
+    /// `Error(E)` to `Error(T)`.
     ///
-    /// If `self` is not `Failure`, `self` is returned.
+    /// If `self` is not `Error`, `self` is returned.
     ///
     /// # Examples
     ///
@@ -548,21 +547,21 @@ impl<S, E, F> Outcome<S, E, F> {
     /// # use rocket::outcome::Outcome;
     /// # use rocket::outcome::Outcome::*;
     /// #
-    /// let x: Outcome<i32, &str, bool> = Failure("hi");
+    /// let x: Outcome<i32, &str, bool> = Error("hi");
     ///
-    /// let mapped = x.failure_then(|v| match v {
-    ///    "hi" => Failure(10),
+    /// let mapped = x.error_then(|v| match v {
+    ///    "hi" => Error(10),
     ///    "test" => Forward(false),
     ///    _ => Success(10)
     /// });
     ///
-    /// assert_eq!(mapped, Failure(10));
+    /// assert_eq!(mapped, Error(10));
     /// ```
     #[inline]
-    pub fn failure_then<T, M: FnOnce(E) -> Outcome<S, T, F>>(self, f: M) -> Outcome<S, T, F> {
+    pub fn error_then<T, M: FnOnce(E) -> Outcome<S, T, F>>(self, f: M) -> Outcome<S, T, F> {
         match self {
             Success(val) => Success(val),
-            Failure(val) => f(val),
+            Error(val) => f(val),
             Forward(val) => Forward(val),
         }
     }
@@ -583,7 +582,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let mapped = x.forward_then(|v| match v {
     ///    Some(true) => Success(10),
     ///    Some(false) => Forward(20),
-    ///    None => Failure("10")
+    ///    None => Error("10")
     /// });
     ///
     /// assert_eq!(mapped, Forward(20));
@@ -592,13 +591,13 @@ impl<S, E, F> Outcome<S, E, F> {
     pub fn forward_then<T, M: FnOnce(F) -> Outcome<S, E, T>>(self, f: M) -> Outcome<S, E, T> {
         match self {
             Success(val) => Success(val),
-            Failure(val) => Failure(val),
+            Error(val) => Error(val),
             Forward(val) => f(val),
         }
     }
 
     /// Converts `Outcome<S, E, F>` to `Result<S, E>` by identity mapping
-    /// `Success(S)` and `Failure(E)` to `Result<T, E>` and mapping `Forward(F)`
+    /// `Success(S)` and `Error(E)` to `Result<T, E>` and mapping `Forward(F)`
     /// to `Result<T, E>` using `f`.
     ///
     /// ```rust
@@ -608,7 +607,7 @@ impl<S, E, F> Outcome<S, E, F> {
     /// let x: Outcome<i32, &str, usize> = Success(10);
     /// assert_eq!(x.ok_map_forward(|x| Ok(x as i32 + 1)), Ok(10));
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("hello");
+    /// let x: Outcome<i32, &str, usize> = Error("hello");
     /// assert_eq!(x.ok_map_forward(|x| Ok(x as i32 + 1)), Err("hello"));
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(0);
@@ -620,13 +619,13 @@ impl<S, E, F> Outcome<S, E, F> {
     {
         match self {
             Outcome::Success(s) => Ok(s),
-            Outcome::Failure(e) => Err(e),
+            Outcome::Error(e) => Err(e),
             Outcome::Forward(v) => f(v),
         }
     }
 
     /// Converts `Outcome<S, E, F>` to `Result<S, E>` by identity mapping
-    /// `Success(S)` and `Forward(F)` to `Result<T, F>` and mapping `Failure(E)`
+    /// `Success(S)` and `Forward(F)` to `Result<T, F>` and mapping `Error(E)`
     /// to `Result<T, F>` using `f`.
     ///
     /// ```rust
@@ -634,21 +633,21 @@ impl<S, E, F> Outcome<S, E, F> {
     /// # use rocket::outcome::Outcome::*;
     /// #
     /// let x: Outcome<i32, &str, usize> = Success(10);
-    /// assert_eq!(x.ok_map_failure(|s| Ok(123)), Ok(10));
+    /// assert_eq!(x.ok_map_error(|s| Ok(123)), Ok(10));
     ///
-    /// let x: Outcome<i32, &str, usize> = Failure("hello");
-    /// assert_eq!(x.ok_map_failure(|s| Ok(123)), Ok(123));
+    /// let x: Outcome<i32, &str, usize> = Error("hello");
+    /// assert_eq!(x.ok_map_error(|s| Ok(123)), Ok(123));
     ///
     /// let x: Outcome<i32, &str, usize> = Forward(0);
-    /// assert_eq!(x.ok_map_failure(|s| Ok(123)), Err(0));
+    /// assert_eq!(x.ok_map_error(|s| Ok(123)), Err(0));
     /// ```
     #[inline]
-    pub fn ok_map_failure<M>(self, f: M) -> Result<S, F>
+    pub fn ok_map_error<M>(self, f: M) -> Result<S, F>
         where M: FnOnce(E) -> Result<S, F>
     {
         match self {
             Outcome::Success(s) => Ok(s),
-            Outcome::Failure(e) => f(e),
+            Outcome::Error(e) => f(e),
             Outcome::Forward(v) => Err(v),
         }
     }
@@ -657,7 +656,7 @@ impl<S, E, F> Outcome<S, E, F> {
     fn formatting(&self) -> (Color, &'static str) {
         match *self {
             Success(..) => (Color::Green, "Success"),
-            Failure(..) => (Color::Red, "Failure"),
+            Error(..) => (Color::Red, "Error"),
             Forward(..) => (Color::Yellow, "Forward"),
         }
     }
@@ -675,7 +674,7 @@ impl<'a, S: Send + 'a, E: Send + 'a, F: Send + 'a> Outcome<S, E, F> {
 
 crate::export! {
     /// Unwraps a [`Success`](Outcome::Success) or propagates a `Forward` or
-    /// `Failure`.
+    /// `Error` by returning early.
     ///
     /// # Syntax
     ///
@@ -691,7 +690,7 @@ crate::export! {
     /// ```
     ///
     /// This is just like `?` (or previously, `try!`), but for `Outcome`. In the
-    /// case of a `Forward` or `Failure` variant, the inner type is passed to
+    /// case of a `Forward` or `Error` variant, the inner type is passed to
     /// [`From`](std::convert::From), allowing for the conversion between
     /// specific and more general types. The resulting forward/error is
     /// immediately returned. Because of the early return, `try_outcome!` can
@@ -746,8 +745,8 @@ crate::export! {
     macro_rules! try_outcome {
         ($expr:expr $(,)?) => (match $expr {
             $crate::outcome::Outcome::Success(val) => val,
-            $crate::outcome::Outcome::Failure(e) => {
-                return $crate::outcome::Outcome::Failure(::std::convert::From::from(e))
+            $crate::outcome::Outcome::Error(e) => {
+                return $crate::outcome::Outcome::Error(::std::convert::From::from(e))
             },
             $crate::outcome::Outcome::Forward(f) => {
                 return $crate::outcome::Outcome::Forward(::std::convert::From::from(f))
diff --git a/core/lib/src/request/from_request.rs b/core/lib/src/request/from_request.rs
index 33aa5ef8..3d048e85 100644
--- a/core/lib/src/request/from_request.rs
+++ b/core/lib/src/request/from_request.rs
@@ -1,3 +1,4 @@
+use std::convert::Infallible;
 use std::fmt::Debug;
 use std::net::{IpAddr, SocketAddr};
 
@@ -12,14 +13,14 @@ use crate::http::uri::{Host, Origin};
 pub type Outcome<S, E> = outcome::Outcome<S, (Status, E), Status>;
 
 impl<S, E> IntoOutcome<S, (Status, E), Status> for Result<S, E> {
-    type Failure = Status;
+    type Error = Status;
     type Forward = Status;
 
     #[inline]
     fn into_outcome(self, status: Status) -> Outcome<S, E> {
         match self {
             Ok(val) => Success(val),
-            Err(err) => Failure((status, err))
+            Err(err) => Error((status, err))
         }
     }
 
@@ -85,8 +86,8 @@ impl<S, E> IntoOutcome<S, (Status, E), Status> for Result<S, E> {
 /// ```
 ///
 /// Request guards always fire in left-to-right declaration order. In the
-/// example above, the order is `a` followed by `b` followed by `c`. Failure is
-/// short-circuiting; if one guard fails, the remaining are not attempted.
+/// example above, the order is `a` followed by `b` followed by `c`. Errors are
+/// short-circuiting; if one guard errors, the remaining are not attempted.
 ///
 /// # Outcomes
 ///
@@ -99,12 +100,12 @@ impl<S, E> IntoOutcome<S, (Status, E), Status> for Result<S, E> {
 ///   the value for the corresponding parameter.  As long as all other guards
 ///   succeed, the request will be handled.
 ///
-/// * **Failure**(Status, E)
+/// * **Error**(Status, E)
 ///
-///   If the `Outcome` is [`Failure`], the request will fail with the given
+///   If the `Outcome` is [`Error`], the request will fail with the given
 ///   status code and error. The designated error [`Catcher`](crate::Catcher)
 ///   will be used to respond to the request. Note that users can request types
-///   of `Result<S, E>` and `Option<S>` to catch `Failure`s and retrieve the
+///   of `Result<S, E>` and `Option<S>` to catch `Error`s and retrieve the
 ///   error value.
 ///
 /// * **Forward**(Status)
@@ -191,7 +192,7 @@ impl<S, E> IntoOutcome<S, (Status, E), Status> for Result<S, E> {
 ///
 ///     The type `T` is derived from the incoming request using `T`'s
 ///     `FromRequest` implementation. If derivation is a `Success`, the value is
-///     returned in `Ok`. If the derivation is a `Failure`, the error value is
+///     returned in `Ok`. If the derivation is an `Error`, the error value is
 ///     returned in `Err`. If the derivation is a `Forward`, the request is
 ///     forwarded with the same status code as the original forward.
 ///
@@ -232,9 +233,9 @@ impl<S, E> IntoOutcome<S, (Status, E), Status> for Result<S, E> {
 ///         }
 ///
 ///         match req.headers().get_one("x-api-key") {
-///             None => Outcome::Failure((Status::BadRequest, ApiKeyError::Missing)),
+///             None => Outcome::Error((Status::BadRequest, ApiKeyError::Missing)),
 ///             Some(key) if is_valid(key) => Outcome::Success(ApiKey(key)),
-///             Some(_) => Outcome::Failure((Status::BadRequest, ApiKeyError::Invalid)),
+///             Some(_) => Outcome::Error((Status::BadRequest, ApiKeyError::Invalid)),
 ///         }
 ///     }
 /// }
@@ -390,7 +391,7 @@ pub trait FromRequest<'r>: Sized {
     /// Derives an instance of `Self` from the incoming request metadata.
     ///
     /// If the derivation is successful, an outcome of `Success` is returned. If
-    /// the derivation fails in an unrecoverable fashion, `Failure` is returned.
+    /// the derivation fails in an unrecoverable fashion, `Error` is returned.
     /// `Forward` is returned to indicate that the request should be forwarded
     /// to other matching routes, if any.
     async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error>;
@@ -398,27 +399,27 @@ pub trait FromRequest<'r>: Sized {
 
 #[crate::async_trait]
 impl<'r> FromRequest<'r> for Method {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         Success(request.method())
     }
 }
 
 #[crate::async_trait]
 impl<'r> FromRequest<'r> for &'r Origin<'r> {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         Success(request.uri())
     }
 }
 
 #[crate::async_trait]
 impl<'r> FromRequest<'r> for &'r Host<'r> {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         match request.host() {
             Some(host) => Success(host),
             None => Forward(Status::NotFound)
@@ -428,9 +429,9 @@ impl<'r> FromRequest<'r> for &'r Host<'r> {
 
 #[crate::async_trait]
 impl<'r> FromRequest<'r> for &'r Route {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         match request.route() {
             Some(route) => Success(route),
             None => Forward(Status::InternalServerError)
@@ -440,18 +441,18 @@ impl<'r> FromRequest<'r> for &'r Route {
 
 #[crate::async_trait]
 impl<'r> FromRequest<'r> for &'r CookieJar<'r> {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         Success(request.cookies())
     }
 }
 
 #[crate::async_trait]
 impl<'r> FromRequest<'r> for &'r Accept {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         match request.accept() {
             Some(accept) => Success(accept),
             None => Forward(Status::NotFound)
@@ -461,9 +462,9 @@ impl<'r> FromRequest<'r> for &'r Accept {
 
 #[crate::async_trait]
 impl<'r> FromRequest<'r> for &'r ContentType {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         match request.content_type() {
             Some(content_type) => Success(content_type),
             None => Forward(Status::NotFound)
@@ -473,9 +474,9 @@ impl<'r> FromRequest<'r> for &'r ContentType {
 
 #[crate::async_trait]
 impl<'r> FromRequest<'r> for IpAddr {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         match request.client_ip() {
             Some(addr) => Success(addr),
             None => Forward(Status::NotFound)
@@ -485,9 +486,9 @@ impl<'r> FromRequest<'r> for IpAddr {
 
 #[crate::async_trait]
 impl<'r> FromRequest<'r> for SocketAddr {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         match request.remote() {
             Some(addr) => Success(addr),
             None => Forward(Status::NotFound)
@@ -497,12 +498,12 @@ impl<'r> FromRequest<'r> for SocketAddr {
 
 #[crate::async_trait]
 impl<'r, T: FromRequest<'r>> FromRequest<'r> for Result<T, T::Error> {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         match T::from_request(request).await {
             Success(val) => Success(Ok(val)),
-            Failure((_, e)) => Success(Err(e)),
+            Error((_, e)) => Success(Err(e)),
             Forward(status) => Forward(status),
         }
     }
@@ -510,21 +511,21 @@ impl<'r, T: FromRequest<'r>> FromRequest<'r> for Result<T, T::Error> {
 
 #[crate::async_trait]
 impl<'r, T: FromRequest<'r>> FromRequest<'r> for Option<T> {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         match T::from_request(request).await {
             Success(val) => Success(Some(val)),
-            Failure(_) | Forward(_) => Success(None),
+            Error(_) | Forward(_) => Success(None),
         }
     }
 }
 
 #[crate::async_trait]
 impl<'r, T: FromRequest<'r>> FromRequest<'r> for Outcome<T, T::Error> {
-    type Error = std::convert::Infallible;
+    type Error = Infallible;
 
-    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+    async fn from_request(request: &'r Request<'_>) -> Outcome<Self, Infallible> {
         Success(T::from_request(request).await)
     }
 }
diff --git a/core/lib/src/response/responder.rs b/core/lib/src/response/responder.rs
index c6fbdd8b..3c1ba956 100644
--- a/core/lib/src/response/responder.rs
+++ b/core/lib/src/response/responder.rs
@@ -111,7 +111,7 @@ use crate::request::Request;
 ///   * An `Ok(Response)` indicates success. The `Response` will be written out
 ///     to the client.
 ///
-///   * An `Err(Status)` indicates failure. The error catcher for `Status` will
+///   * An `Err(Status)` indicates an error. The error catcher for `Status` will
 ///     be invoked to generate a response.
 ///
 /// # Implementation Tips
diff --git a/core/lib/src/route/handler.rs b/core/lib/src/route/handler.rs
index 9fee0d67..d139942b 100644
--- a/core/lib/src/route/handler.rs
+++ b/core/lib/src/route/handler.rs
@@ -141,7 +141,7 @@ pub trait Handler: Cloneable + Send + Sync + 'static {
     /// The variant of `Outcome` returned by the returned `Future` determines
     /// what Rocket does next. If the return value is a `Success(Response)`, the
     /// wrapped `Response` is used to respond to the client. If the return value
-    /// is a `Failure(Status)`, the error catcher for `Status` is invoked to
+    /// is an `Error(Status)`, the error catcher for `Status` is invoked to
     /// generate a response. Otherwise, if the return value is `Forward(Data)`,
     /// the next matching route is attempted. If there are no other matching
     /// routes, the `404` error catcher is invoked.
@@ -172,7 +172,7 @@ impl<'r, 'o: 'r> Outcome<'o> {
     /// Return the `Outcome` of response to `req` from `responder`.
     ///
     /// If the responder returns `Ok`, an outcome of `Success` is returned with
-    /// the response. If the responder returns `Err`, an outcome of `Failure` is
+    /// the response. If the responder returns `Err`, an outcome of `Error` is
     /// returned with the status code.
     ///
     /// # Example
@@ -188,14 +188,14 @@ impl<'r, 'o: 'r> Outcome<'o> {
     pub fn from<R: Responder<'r, 'o>>(req: &'r Request<'_>, responder: R) -> Outcome<'r> {
         match responder.respond_to(req) {
             Ok(response) => Outcome::Success(response),
-            Err(status) => Outcome::Failure(status)
+            Err(status) => Outcome::Error(status)
         }
     }
 
     /// Return the `Outcome` of response to `req` from `responder`.
     ///
     /// If the responder returns `Ok`, an outcome of `Success` is returned with
-    /// the response. If the responder returns `Err`, an outcome of `Failure` is
+    /// the response. If the responder returns `Err`, an outcome of `Error` is
     /// returned with the status code.
     ///
     /// # Example
@@ -214,7 +214,7 @@ impl<'r, 'o: 'r> Outcome<'o> {
         let responder = result.map_err(crate::response::Debug);
         match responder.respond_to(req) {
             Ok(response) => Outcome::Success(response),
-            Err(status) => Outcome::Failure(status)
+            Err(status) => Outcome::Error(status)
         }
     }
 
@@ -243,8 +243,8 @@ impl<'r, 'o: 'r> Outcome<'o> {
         }
     }
 
-    /// Return an `Outcome` of `Failure` with the status code `code`. This is
-    /// equivalent to `Outcome::Failure(code)`.
+    /// Return an `Outcome` of `Error` with the status code `code`. This is
+    /// equivalent to `Outcome::Error(code)`.
     ///
     /// This method exists to be used during manual routing.
     ///
@@ -255,12 +255,12 @@ impl<'r, 'o: 'r> Outcome<'o> {
     /// use rocket::http::Status;
     ///
     /// fn bad_req_route<'r>(_: &'r Request, _: Data<'r>) -> route::Outcome<'r> {
-    ///     route::Outcome::failure(Status::BadRequest)
+    ///     route::Outcome::error(Status::BadRequest)
     /// }
     /// ```
     #[inline(always)]
-    pub fn failure(code: Status) -> Outcome<'r> {
-        Outcome::Failure(code)
+    pub fn error(code: Status) -> Outcome<'r> {
+        Outcome::Error(code)
     }
 
     /// Return an `Outcome` of `Forward` with the data `data`. This is
diff --git a/core/lib/src/route/route.rs b/core/lib/src/route/route.rs
index 24853d95..e78275b9 100644
--- a/core/lib/src/route/route.rs
+++ b/core/lib/src/route/route.rs
@@ -64,7 +64,7 @@ use crate::sentinel::Sentry;
 /// higher precedence during routing than routes with higher ranks. Thus, routes
 /// are attempted in ascending rank order. If a higher precedence route returns
 /// an `Outcome` of `Forward`, the next highest precedence route is attempted,
-/// and so on, until a route returns `Success` or `Failure`, or there are no
+/// and so on, until a route returns `Success` or `Error`, or there are no
 /// more routes to try. When all routes have been attempted, Rocket issues a
 /// `404` error, handled by the appropriate [`Catcher`](crate::Catcher).
 ///
diff --git a/core/lib/src/serde/json.rs b/core/lib/src/serde/json.rs
index dfc85a6b..a96f629e 100644
--- a/core/lib/src/serde/json.rs
+++ b/core/lib/src/serde/json.rs
@@ -201,12 +201,12 @@ impl<'r, T: Deserialize<'r>> FromData<'r> for Json<T> {
         match Self::from_data(req, data).await {
             Ok(value) => Outcome::Success(value),
             Err(Error::Io(e)) if e.kind() == io::ErrorKind::UnexpectedEof => {
-                Outcome::Failure((Status::PayloadTooLarge, Error::Io(e)))
+                Outcome::Error((Status::PayloadTooLarge, Error::Io(e)))
             },
             Err(Error::Parse(s, e)) if e.classify() == serde_json::error::Category::Data => {
-                Outcome::Failure((Status::UnprocessableEntity, Error::Parse(s, e)))
+                Outcome::Error((Status::UnprocessableEntity, Error::Parse(s, e)))
             },
-            Err(e) => Outcome::Failure((Status::BadRequest, e)),
+            Err(e) => Outcome::Error((Status::BadRequest, e)),
 
         }
     }
diff --git a/core/lib/src/serde/msgpack.rs b/core/lib/src/serde/msgpack.rs
index e77c6aa7..3b92f060 100644
--- a/core/lib/src/serde/msgpack.rs
+++ b/core/lib/src/serde/msgpack.rs
@@ -170,15 +170,15 @@ impl<'r, T: Deserialize<'r>> FromData<'r> for MsgPack<T> {
         match Self::from_data(req, data).await {
             Ok(value) => Outcome::Success(value),
             Err(Error::InvalidDataRead(e)) if e.kind() == io::ErrorKind::UnexpectedEof => {
-                Outcome::Failure((Status::PayloadTooLarge, Error::InvalidDataRead(e)))
+                Outcome::Error((Status::PayloadTooLarge, Error::InvalidDataRead(e)))
             },
             | Err(e@Error::TypeMismatch(_))
             | Err(e@Error::OutOfRange)
             | Err(e@Error::LengthMismatch(_))
             => {
-                Outcome::Failure((Status::UnprocessableEntity, e))
+                Outcome::Error((Status::UnprocessableEntity, e))
             },
-            Err(e) => Outcome::Failure((Status::BadRequest, e)),
+            Err(e) => Outcome::Error((Status::BadRequest, e)),
         }
     }
 }
diff --git a/core/lib/src/serde/uuid.rs b/core/lib/src/serde/uuid.rs
index 8e664657..8c377168 100644
--- a/core/lib/src/serde/uuid.rs
+++ b/core/lib/src/serde/uuid.rs
@@ -79,7 +79,7 @@
 use crate::request::FromParam;
 use crate::form::{self, FromFormField, ValueField};
 
-/// Error returned on [`FromParam`] or [`FromFormField`] failure.
+/// Error returned on [`FromParam`] or [`FromFormField`] failures.
 ///
 pub use uuid_::Error;
 
diff --git a/core/lib/src/server.rs b/core/lib/src/server.rs
index e3836984..e874b0ff 100644
--- a/core/lib/src/server.rs
+++ b/core/lib/src/server.rs
@@ -114,7 +114,7 @@ async fn hyper_service_fn(
 }
 
 impl Rocket<Orbit> {
-    /// Wrapper around `_send_response` to log a success or failure.
+    /// Wrapper around `_send_response` to log a success or error.
     #[inline]
     async fn send_response(
         &self,
@@ -290,12 +290,12 @@ impl Rocket<Orbit> {
                 request._set_method(Method::Get);
                 match self.route(request, data).await {
                     Outcome::Success(response) => response,
-                    Outcome::Failure(status) => self.handle_error(status, request).await,
+                    Outcome::Error(status) => self.handle_error(status, request).await,
                     Outcome::Forward((_, status)) => self.handle_error(status, request).await,
                 }
             }
             Outcome::Forward((_, status)) => self.handle_error(status, request).await,
-            Outcome::Failure(status) => self.handle_error(status, request).await,
+            Outcome::Error(status) => self.handle_error(status, request).await,
         };
 
         // Set the cookies. Note that error responses will only include cookies
@@ -310,7 +310,7 @@ impl Rocket<Orbit> {
 
     /// Tries to find a `Responder` for a given `request`. It does this by
     /// routing the request and calling the handler for each matching route
-    /// until one of the handlers returns success or failure, or there are no
+    /// until one of the handlers returns success or error, or there are no
     /// additional routes to try (forward). The corresponding outcome for each
     /// condition is returned.
     #[inline]
@@ -329,14 +329,14 @@ impl Rocket<Orbit> {
 
             let name = route.name.as_deref();
             let outcome = handle(name, || route.handler.handle(request, data)).await
-                .unwrap_or(Outcome::Failure(Status::InternalServerError));
+                .unwrap_or(Outcome::Error(Status::InternalServerError));
 
             // Check if the request processing completed (Some) or if the
             // request needs to be forwarded. If it does, continue the loop
             // (None) to try again.
             info_!("{} {}", "Outcome:".primary().bold(), outcome);
             match outcome {
-                o@Outcome::Success(_) | o@Outcome::Failure(_) => return o,
+                o@Outcome::Success(_) | o@Outcome::Error(_) => return o,
                 Outcome::Forward(forwarded) => (data, status) = forwarded,
             }
         }
@@ -380,7 +380,7 @@ impl Rocket<Orbit> {
 
     // Invokes the catcher for `status`. Returns the response on success.
     //
-    // On catcher failure, the 500 error catcher is attempted. If _that_ fails,
+    // On catcher error, the 500 error catcher is attempted. If _that_ errors,
     // the (infallible) default 500 error cather is used.
     pub(crate) async fn handle_error<'s, 'r: 's>(
         &'s self,
diff --git a/core/lib/src/state.rs b/core/lib/src/state.rs
index 6b5edcdf..9ecf24e1 100644
--- a/core/lib/src/state.rs
+++ b/core/lib/src/state.rs
@@ -202,7 +202,7 @@ impl<'r, T: Send + Sync + 'static> FromRequest<'r> for &'r State<T> {
             Some(state) => Outcome::Success(state),
             None => {
                 error_!("Attempted to retrieve unmanaged state `{}`!", type_name::<T>());
-                Outcome::Failure((Status::InternalServerError, ()))
+                Outcome::Error((Status::InternalServerError, ()))
             }
         }
     }
diff --git a/examples/manual-routing/src/main.rs b/examples/manual-routing/src/main.rs
index 704b69c7..2da4c42a 100644
--- a/examples/manual-routing/src/main.rs
+++ b/examples/manual-routing/src/main.rs
@@ -38,7 +38,7 @@ fn upload<'r>(req: &'r Request, data: Data<'r>) -> route::BoxFuture<'r> {
     Box::pin(async move {
         if !req.content_type().map_or(false, |ct| ct.is_plain()) {
             println!("    => Content-Type of upload must be text/plain. Ignoring.");
-            return route::Outcome::failure(Status::BadRequest);
+            return route::Outcome::error(Status::BadRequest);
         }
 
         let path = req.rocket().config().temp_dir.relative().join("upload.txt");
@@ -49,10 +49,10 @@ fn upload<'r>(req: &'r Request, data: Data<'r>) -> route::BoxFuture<'r> {
             }
 
             println!("    => Failed copying.");
-            route::Outcome::failure(Status::InternalServerError)
+            route::Outcome::error(Status::InternalServerError)
         } else {
             println!("    => Couldn't open file: {:?}", file.unwrap_err());
-            route::Outcome::failure(Status::InternalServerError)
+            route::Outcome::error(Status::InternalServerError)
         }
     })
 }
diff --git a/site/guide/4-requests.md b/site/guide/4-requests.md
index 1a1a8c63..56b927ce 100644
--- a/site/guide/4-requests.md
+++ b/site/guide/4-requests.md
@@ -263,7 +263,7 @@ would never forward. An `Ok` variant would indicate that `<id>` was a valid
 ! tip: It's not just forwards that can be caught!
 
   In general, when any guard fails for any reason, including parameter guards,
-  you can use an `Option` or `Result` type in its place to catch the failure.
+  you can use an `Option` or `Result` type in its place to catch the error.
 
 By the way, if you were to omit the `rank` parameter in the `user_str` or
 `user_int` routes, Rocket would emit an error and abort launch, indicating that
@@ -353,7 +353,7 @@ fn index(param: isize, a: A, b: B, c: C) { /* ... */ }
 ```
 
 Request guards always fire in left-to-right declaration order. In the example
-above, the order will be `A` followed by `B` followed by `C`. Failure is
+above, the order will be `A` followed by `B` followed by `C`. Errors are
 short-circuiting; if one guard fails, the remaining are not attempted. To learn
 more about request guards and implementing them, see the [`FromRequest`]
 documentation.
@@ -484,7 +484,7 @@ The three routes above encode authentication _and_ authorization. The
 the admin panel displayed. If the user is not an admin, the `AdminUser` guard
 will forward. Since the `admin_panel_user` route is ranked next highest, it is
 attempted next. This route succeeds if there is _any_ user signed in, and an
-authorization failure message is displayed. Finally, if a user isn't signed in,
+authorization error message is displayed. Finally, if a user isn't signed in,
 the `admin_panel_redirect` route is attempted. Since this route has no guards,
 it always succeeds. The user is redirected to a log in page.
 
@@ -522,7 +522,7 @@ If the `User` guard forwards or fails, the `Option` will be `None`. If it
 succeeds, it will be `Some(User)`.
 
 For guards that may fail (and not just forward), the `Result<T, E>` guard allows
-retrieving the error type `E` on failure. As an example, when the
+retrieving the error type `E` on error. As an example, when the
 [`mtls::Certificate`] type fails, it reports the reason in an [`mtls::Error`]
 type. The value can be retrieved in a handler by using a `Result<Certificate,
 Error>` guard:
@@ -876,7 +876,7 @@ fields implement [`FromForm`], or equivalently, [`FromFormField`].
 If a `POST /todo` request arrives, the form data will automatically be parsed
 into the `Task` structure. If the data that arrives isn't of the correct
 Content-Type, the request is forwarded. If the data doesn't parse or is simply
-invalid, a customizable error is returned. As before, a forward or failure can
+invalid, a customizable error is returned. As before, a forward or error can
 be caught by using the `Option` and `Result` types:
 
 ```rust
diff --git a/site/guide/5-responses.md b/site/guide/5-responses.md
index 2a388950..56656d91 100644
--- a/site/guide/5-responses.md
+++ b/site/guide/5-responses.md
@@ -289,7 +289,7 @@ fn handler() -> &'static str {
 
 `Option` is a _wrapping_ responder: an `Option<T>` can only be returned when `T`
 implements `Responder`. If the `Option` is `Some`, the wrapped responder is used
-to respond to the client. Otherwise, a error of **404 - Not Found** is returned
+to respond to the client. Otherwise, an error of **404 - Not Found** is returned
 to the client.
 
 This implementation makes `Option` a convenient type to return when it is not
diff --git a/site/tests/src/lib.rs b/site/tests/src/lib.rs
index 33114eee..2bf0a0b2 100644
--- a/site/tests/src/lib.rs
+++ b/site/tests/src/lib.rs
@@ -26,7 +26,7 @@ macro_rules! assert_form_parses {
             Ok(v) => assert_eq!(v, $value, "{}", $form),
             Err(e) => {
                 eprintln!("form failed to parse\n> form: {:?}\n> error: {:?}", $form, e);
-                panic!("form parse failure");
+                panic!("form parse error");
             }
         }
     );