Since we can pass an object to jQuery.Callbacks now, let's name it options to...

Since we can pass an object to jQuery.Callbacks now, let's name it options to be consistent with the rest of the code.

src/callbacks.js

 (function( jQuery ) {
 
-// String to Object flags format cache
-var flagsCache = {};
+// String to Object options format cache
+var optionsCache = {};
 
-// Convert String-formatted flags into Object-formatted ones and store in cache
-function createFlags( flags ) {
-	var object = flagsCache[ flags ] = {},
+// Convert String-formatted options into Object-formatted ones and store in cache
+function createOptions( options ) {
+	var object = optionsCache[ options ] = {},
 		i, length;
-	flags = flags.split( /\s+/ );
-	for ( i = 0, length = flags.length; i < length; i++ ) {
-		object[ flags[i] ] = true;
+	options = options.split( /\s+/ );
+	for ( i = 0, length = options.length; i < length; i++ ) {
+		object[ options[i] ] = true;
 	}
 	return object;
 }
@@ -17,13 +17,13 @@ function createFlags( flags ) {
 /*
  * Create a callback list using the following parameters:
  *
- *	flags:	an optional list of space-separated flags that will change how
- *			the callback list behaves
+ *	options: an optional list of space-separated options that will change how
+ *			the callback list behaves or a more traditional option object
  *
  * By default a callback list will act like an event callback list and can be
  * "fired" multiple times.
  *
- * Possible flags:
+ * Possible options:
  *
  *	once:			will ensure the callback list can only be fired once (like a Deferred)
  *
@@ -36,11 +36,13 @@ function createFlags( flags ) {
  *	stopOnFalse:	interrupt callings when a callback returns false
  *
  */
-jQuery.Callbacks = function( flags ) {
+jQuery.Callbacks = function( options ) {
 
-	// Convert flags from String-formatted to Object-formatted if needed
+	// Convert options from String-formatted to Object-formatted if needed
 	// (we check in cache first)
-	flags = typeof flags === "string" ? ( flagsCache[ flags ] || createFlags( flags ) ) : jQuery.extend( {}, flags );
+	options = typeof options === "string" ?
+		( optionsCache[ options ] || createOptions( options ) ) :
+		jQuery.extend( {}, options );
 
 	var // Actual callback list
 		list = [],
@@ -73,7 +75,7 @@ jQuery.Callbacks = function( flags ) {
 					add( elem );
 				} else if ( type === "function" ) {
 					// Add if not in unique mode and callback is not in
-					if ( !flags.unique || !self.has( elem ) ) {
+					if ( !options.unique || !self.has( elem ) ) {
 						list.push( elem );
 					}
 				}
@@ -82,21 +84,21 @@ jQuery.Callbacks = function( flags ) {
 		// Fire callbacks
 		fire = function( context, args ) {
 			args = args || [];
-			memory = !flags.memory || [ context, args ];
+			memory = !options.memory || [ context, args ];
 			fired = true;
 			firing = true;
 			firingIndex = firingStart || 0;
 			firingStart = 0;
 			firingLength = list.length;
 			for ( ; list && firingIndex < firingLength; firingIndex++ ) {
-				if ( list[ firingIndex ].apply( context, args ) === false && flags.stopOnFalse ) {
+				if ( list[ firingIndex ].apply( context, args ) === false && options.stopOnFalse ) {
 					memory = true; // Mark as halted
 					break;
 				}
 			}
 			firing = false;
 			if ( list ) {
-				if ( !flags.once ) {
+				if ( !options.once ) {
 					if ( stack && stack.length ) {
 						memory = stack.shift();
 						self.fireWith( memory[ 0 ], memory[ 1 ] );
@@ -151,7 +153,7 @@ jQuery.Callbacks = function( flags ) {
 								list.splice( i--, 1 );
 								// If we have some unicity property then
 								// we only need to do this once
-								if ( flags.unique ) {
+								if ( options.unique ) {
 									break;
 								}
 							}
@@ -203,10 +205,10 @@ jQuery.Callbacks = function( flags ) {
 			fireWith: function( context, args ) {
 				if ( stack ) {
 					if ( firing ) {
-						if ( !flags.once ) {
+						if ( !options.once ) {
 							stack.push( [ context, args ] );
 						}
-					} else if ( !( flags.once && memory ) ) {
+					} else if ( !( options.once && memory ) ) {
 						fire( context, args );
 					}
 				}