leetspeak for a youtube troll. Like a cancerous tumor, the ut00m3r is renowned for trolling comments, being flippant because he was beaten to the posting, or basically has nothing constructive to say. Also see YouTube hater.
#313: That vid was soooo awesome!! I'd like to see more of Dubya getting his 455 handed to him by that circus monkey. Ex-presidents mud-wrestling animals is the shet!
#troll: Your video's stupid!
#313: STFU ut00m3r!