ball clapping is when your nuts hit right between your dick and your ass. usually makes a loud noise when hitting, especially when sweaty! Tends to happen during sexual intrercorse, and when jacking off.
When I was screwing this hot chick, I could hear my balls clapping!!!
The sound it makes when you get hit in the balls, usually meaning there was a good connection.
I meant to kick Dillon in the ass, but I went to far and kicked him in the balls, I heard the ball clap and I knew he was down for the count.