Used in playing Super Smash Brothers Melee; sort of like revenge, but better. Example: Zelda kills Roy with a lucky but annoying shitty item such as a Mr. Saturn, then Roy comes back and Makes Zelda's life a living hell. Zelda is then bained. Roy bained Zelda.
Taylor: GOD DAMN IT STOP BAINING ME!
George: Sorry dude, I can't stop, I'm stuck in kick your ass mode