Someone who is attracted to buttholes. They can be either male or female buttholes. It is used in the same way you would use the word bisexual or homosexual.
Jack: Didn't you hear? Mary did Mark in the ass!
David: She did Jenna is the ass last week! I thought she was a lesbian?
Jack: No, she's just an analsexual.
Analsexual is a term used for a male who claims to be straight, but sticks random cylinder-shaped objects in his rectum. He is usually about 13-20 years old, and he doesn't stick things in his butt to get pleasure. He usually inserts things in his butt to get others to laugh, or create a fun, amusing atmosphere. He usually does this ritual only in front of close peers and friends. Sometimes after the object is inserted into his rectum, such as a carrot, he'll consume the poop-covered object. An analsexual is usually not gay, but many think he is. Some things that can be inserted in to the rectum are carrots, markers, peanuts (in the shell), drumsticks, licorice, and regular tree twigs.
Dude: Kick-ass did you hear about what that Adam kid did?!
Kick-ass: No! What'd he do?
Dude: He stuck a corndog up his ass!
Kick-ass: Holy shit Dude! He must be gay!
Dude: No... he's banged a bunch of girls. I think he's just analsexual.