To build carriers you have to tech quite a bit, and a single carrier takes much to be produced. Hence, you cannot "rush" with carriers.
Now used to describe any n00b tactics, or when someone completes a task by swarming the enemy. See zerg.
n00b: Uh... erm... CARRIER RUSH!
1337 haxor: Oh noes! I've been pwned by a fucking n00b! ;-;