SD

Basically a term for rage quit, but commonly for games like Super Smash Bros. You basically either gave up because someone else is better at the game, or you sacrificed yourself to kill someone else in-game.

"Dude, why did you SD?"
"You're being an asshole to the other gamers and I don't want to deal with that bs."
"Dude...It's just a game. You just lost the game because you're being stupid."
"Whatever."