Generally used as an insult. An expression of disgust, likening the object to hair clumped around the anus with faeces or fecal matter.
Shut up you assclump!
The clump of sweaty shit that gets stuck in between your asscheeks by your wooly-mammoth like asshairs.
John: Hello kind fellow. Would you mind tearing out an assclump for me? It's been bothering me all day.
Austin: Why of course, I was actually going to stop for breakfast, but this'll do. Cheerio!