What a Billy Share definition Flag The act of KSING a team player on purpose non stop and denying it. When you get the KS, you scream WHAT A BILLY in an Irish accent. Genius. Player1: OMG MAN U KSED ME SO BAD!!!You: WHAT A BILLY What a Billy by lalalalaerkliergn December 10, 2010 Get the What a Billy mug.