An expression derived from mathematics (x2 ; x = times, 2 = two). It is used to express agreement or accordance, but to exemplify your feeling towards it are doubled. It should be used with a small x (x not X).
Dude1 "Man this game is teh suck!"
Dude2 "x2, let's play WoW instead."
Dude1 "God I hate that Lokus! I wish he would get booted from the guild!"