A thunder clap is when your girl goes down on your dick on last time and you nut. They call it the thunder clap for 2 reasons. 1. That's the sound her butt makes, 2. You pass out and see lightning strikes for 5 minutes

When yo girl slam it down so hard on the last stroke that her cheeks clap against you while you pass out from nuttin.

Its when a woman is bouncing her ass of your dick and at the same time as you nut her booty cheeks clap on your dick. Its said that when that happens the male orgasm is so powerful you'll see thunder.

When thy sweaty thighs smack against thy sweaty scrotum .