The action of having sex with a girl on her period and, subsequently, slapping her on the forehead with your, now blood covered, penis. This action causes the girl to look like she was brutally bludgeoned, but, in fact, has just engaged in some good ol' fashioned fun.
"Did you see those pics of Sylvia?! She looked like she got her head bashed in!!"
"No way man, she was just given the old bloody bludgeon. Look, shes smiling in the picture."