is the process of a male inserting both his erect penis and both testicles into the arse of a participating female of any species. When the bloke is about to cum, the Shally Whacking commences: the bloke rips his penis and balls out of her arse, and slaps her arse cheeks with his penis whilst cumming everywhere.
Tim "she's a dirty cunt"
Laura "how do you know?"
Tim "she said I can Shally Whack her any day"
Emma "my arse hurts"
Mark "I should fucking think so too! That'll be all the Shally Whacking"
Tim "my balls feel/smell like shit"
Emma "that'll be all the Shally Whacking. wash them you dirty bastard."