A rude person that interrupts people and speaks over them if they don't concede to being interrupted. They generally have a disregard for anything others are talking about. They are known to be loud, obnoxious, and generally inconsiderate of normal social-speaking etiquette. They do this in such a fashion that others wonder if they have ADHD, Tourette's Syndrome or some other mental disorder that makes them incapable of carrying on a conversation, instead turning it into a monologue.
Matt: "Hey, man. You gonna go over to ........(Inaudible because Drew is talking loudly and incessantly about another subject altogether)....... on New Year's Eve?"
Drew: (Overtop of Matt, loudly, and totally off subject)....."Man, I remember the other day I was at 7-11, there was a whole gang of hotties there buying beer and what not!"
Matt: Did you hear I thing I said? Guess not, you're too busy being a rude-ass overtalker.