Editing WoW:Cooldown (section)

== Global cooldown  ==
A global or universal cooldown, frequently shortened to "GCD", is the cooldown which starts every time you start to cast a spell, and it affects all of your class spells. There are exceptions to this, however, as noted below. The basic rule of thumb is that if the spell affects the casting of the next spell, it will not activate the global cooldown.

If the spell has a casting time less than the global cooldown (or instant cast), you generally have to wait the remainder of the global cooldown. If a spell with casting time is interrupted before it has finished casting, the global cooldown will be canceled, meaning you can start casting a new one immediately.

The global cooldown is generally 1.5 seconds for all classes except rogues, Cat Form druids, and Death Knights, whose abilities are mostly one second global cooldown(reduced to 0.5 in UP). Shaman totems also only trigger a one second global cooldown as well as warlock curses with Amplify Curse. The global cooldown affects the wait for the next ability, so using an item or ability with the standard 1.5 second cooldown will require waiting that long before a 1 second global cooldown ability can be used.