A person, male or female, without any "junk in the trunk." A prevelant trait in skinny individuals. The opposite of a ghetto booty or bubble butt in women, but also used to describe males (unlike ghetto booty or bubble butt, which tend to solely describe the female body).
Man, did you see that girl?
-Yeah, she's got a nice body. Her friend would be the complete package too, if not for that wall butt!
I want a guy that I can grab onto. No wall butts.