Can refer to someone being killed or can refer to someone having nasty hardcore sex thus making a hard thumping noise which can resemble someone clapping their hands.
Like some clap on lights in this bitch
I'm a be clapping all night in this bitch
--Lil Wayne(Got Money)
When you defend/hate/infatuated with a person or so passionately you seem to be sucking one’s meat to the point their balls are clapping against your chin.
Stop clapping you don’t even know him personally , how would you know?
"Clappin" is the act of having sexual relations with another person. This Word was originally used by metalheads from Berkeley California. See O.G. Bootyclap