Someone who exhibits lame tactics in competitive sports video games, usually against a human opponent. This could include but is not limited to running the same play over and over, using clock tactics, or anything else that isn't in the spirit of friends sitting down to waste time playing video games.
Player: "Man you're milking the clock in a video game? That's fucking twatballing, man"
Player: "Quit pressing pause in the middle of my play, you fucking twatballer"
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.