When you see a girl who is way hotter than the guy she is with, you know she must have lost a bet to be dating him. This unproportionately hot girlfriend is a Loserbet.
Guy 1) "Damn, that girl is smoking!"
Guy 2) "Wait, wait! That guy behind her.. is he her boyfriend?!"
Guy 1) No way man. He couldn't possibly.."
Guy 2) Woah! He just kissed her!