Cooldown: n. MMO-related. A period of wait time before a spell, ability or power can be used after that same spell, ability, or power has been used.
Example: In World of Warcraft, a character’s hearthstone has a one hour cooldown. Once you use it to teleport back to your ‘home’ location, the stone cannot be used again for an hour.
Global Cooldown: n. MMO-related. A period of wait time before any spell, ability or power can be used after ANY OTHER spell, ability, or power has been used.
Example 1: In World of Warcraft, any attack power triggers the ‘global cooldown’. At the moment that an attack power occurs, all other special abilities become unavailable for 1.5 seconds. This is to prevent players from stacking up skill uses at an unrealistic or game-breaking rate.
Example 2: In City of Heroes and Lord of the Rings online, the Global Cooldown is actually ‘front loaded’ into each power — there is a (often uninterruptible) delay between activating an attack and that attack actually happening. The end result is the same as WoWs global cooldown, but allows players to queue their next attack while the current attack is still ‘going’.
Global Cooldown: n. Doyce-related. A period of time during which I need to decompress at the end of the day. Cooldown times vary, depending on what has been happening that day. Cooldowns often include use of an MMO, but might also involve reading, watching videos, or various other activities; however, many people adopt specific activities that they prefer, and are reluctant to change.
Failure to observe the the Global Cooldown can be game-breaking.
Global Cooldowns (as defined here) are strongly affected by who else is in your adventuring party, as other players can aid the GCD, extend the time required, or even interrupt the GCD unknowingly, resulting in a number of system errors.
Communicating with the other members of your team about the GCD is highly recommended, especially when you have recently added a new member to your party.