1. A troll who frequents the same chat room/game room with the express intent to annoy the regulars with ilk, foul language and total disgust and rudeness. Usually said assclown will end up getting the perma-mute by everyone.
2. In general, on the society totem pole, someone who is lower than an asshole or jack ass.
Oh christ, the assclown is back. Mute now to avoid feeding the troll.
Assclown is possibly the worst insult you could give a person, and is in most cases synonymous with "failure at life."
"You're an assclown, Val."