The
Boston Backslap is the sexual act of rooting doggy-style and the
male pretends to be
edging near to climax, instead shitting into his hand and slapping it on the females back.
Billy: Bro I was
fucking that dog of a cunt Deanna, and she was a shit root so I shit in my
hand and slapped it on her back.
Joey: So you
Boston Backslapped her cunt?
Billy: Yeah, I only found out after she was your mrs though....