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."
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.