Vagina. Yes, its hilarious way to define it, but whatever. Its literally the "buisness" of a lady...and men. Or occasionally other women. Thought up by the wonderful T***a of ******* School of ********** and *********** *******.
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