Getting hit in the nuts
O my God, that dude just gave me a knuller
knuller -s, -ing (also chnuller)
1. a person who have casual sex with anyone at anytime.
2. Two persons living together just for the sex, without any other commitments
1. Lisa is such a knuller! She goes to bed with anyone!
2. George and Jennie are not married! They are just knullers!