Stands for "get that shit outta here." Used when someone says something somewhat insulting but primarily annoying. It tells the other person that he or she should stop being stupid and annoying, or else leave.
Irreverent_Player: hi dude
DragonDude18193: hey, what happened to your armor?
Irreverent_Player: i lost it in a duel
DragonDude18193: LOL HAHA NOOB!!!