A lovely retort when someone is acting like a douchebag and a complete idiot - i.e. boob/tit. A very convenient word, and should be included in many college students' vocabularies. It gets to the point, and leaves people shocked as to how to respond.
Zach: Dude, you're such a douchetit.
Bill: *Silence, and embarrassment as he runs out of the room crying like the bitch that he is*