noun: droopy, wrinkled, testicles that belong to a man 45 years or older. Just the thought of old man balls (more commonly referred to as O.M.B.) is enough to make you shudder with disgust.
Girl 1: "So, how is Paul in bed?"
Girl 2: "Oh man, he was turning me on and all, but then I saw his Old Man Balls (O.M.B.), and I would have needed to do some meth to get on that!"