Short for Gretrieg i.e. the douchebag who ruined DragonRealms: The Fallen (a pvp server) by spending thousands and thousands of dollars to acquire dozens of high level characters with which to zerg his enemies; for he sucked mightily at pvp. Using this tactic he was successful at driving most veteran players from the game.
"Who is the most pathetic person you've ever come across in an MMORPG? Let me tell you about gret"