Eating another person's ass to provide sexual pleasure. Usually a result of a large chemical or alcohol intake that leaves you feeling so wild and horny you just wanna do EVERYTHING.
I came home from that kegger and I was so blotto I think I performed rumpilingus on my girl.
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