When a man is a.) naked or b.) wearing clothing that is non-constraining on the crotchal region, and he begins pelvic thrusting with such violent determination that his scroat (scrotum) begins to repeatedly smack audibly againnt his chode/taint/chonch.
Honey, stop that! Your thunder clap so goddamn loud it's going to wake the neighbors again.
The name given to the slapping sound produced during the act of sexual intercourse in the famed doggy style position when a males testicles, which are especially loose and/or saggy due to heat or over stimulation, smack against the back of the females thigh and produce a slapping sound reminiscent of a soft clap of the hands.
Man 1 "Nigga i was bangin my girl the other night doggy style and my balls were so loose that the sound of the thunderclap was proper so loud that i went deaf in my left ear."
Man 2 "Shit nigga you best calm down on swingin dem testiclots around."