A sexual act involving one woman and three men. One of the men penetrates the woman in the vagina and the other two penetrate her anus.
Named so because of the line in the song "Incredibad" from The Lonely Island's album of the same title, "One in the front and two in the back."
Guy #1: Hey, ever wondered what it'd be like to have sex Incredibad Style?
Guy #2: Yeah, ever since I heard that song... Shall we ask Steve to do it with us?
Guy #1: If you must. We need to find a girl first though otherwise it's gonna turn out Incredigay!
Guy #2: No. Just no. *shakes head*