>>40303111It's a black term that's been co-opted by white internet users. "To clap" means to strike, which likely is a shortening of "to clap cheeks", meaning to fuck someone in the ass, or to spank them. I'm not sure which one. Either way, the meaning has been reduced to meaning "to beat someone", so to "clap back" just is a black way of saying "to strike back", frequently used by cringe inducing white people.
