1. A very boastful and talkative person; a braggart
2. A self-important egomaniac who likes to toot his own horn, like those assholes who put bumper stickers on their cars that say "PROUD PARENTS OF AN HONOR STUDENT AT (blah blah blah) HIGH SCHOOL"
A wanker who argues until you admit he's right just to get him to shut up. Also has problems with sexuality.
Person 1: Hey I heard you have problems getting attracted to girls?
Bowmar: Well, it is possible to not be attracted to girls nor men but not to be asexual.
Person 1: That's true - as long as you shut up.