--- a/dom/webidl/PrecompiledScript.webidl
+++ b/dom/webidl/PrecompiledScript.webidl
@@ -1,23 +1,24 @@
 /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
 /**
- * Represents a pre-compiled JS script, which can be repeatedly exeuted in
+ * Represents a pre-compiled JS script, which can be repeatedly executed in
  * different globals without being re-parsed.
  */
 [ChromeOnly, Exposed=(Window,System)]
 interface PrecompiledScript {
   /**
-   * Executes the script in the global of the given object, and returns the
-   * value of its last expression, if compiled with a return value.
+   * Executes the script in the context of, and with the security principal
+   * of, the given object's global. If compiled with a return value, returns
+   * the value of the script's last expression. Otherwise returns undefined.
    */
   [Throws]
   any executeInGlobal(object global);
 
   /**
    * The URL that the script was loaded from.
    */
   [Pure]