When a woman masturbates while she's having her period. The word is coined from the words "masturbation" and "menstruation(i.e. when a woman has her period).
When the voyeur caught sight of the black-haired, pale-skinned goth chick lying naked and menstrubating on a towel on the floor, he immediately thought to himself, "That is one sick bitch!"
Mark H. Expanding the sexual slang vocabulary since February 2004.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi