When you don't wipe quite good enough, and you're left with that greasy, dirty, sweaty ass-crack feeling. Especially common on hot and humid days.
Joey was too lazy to scrub his ass properly. Now, he's running around with a hot, sweaty, and uncomfortable moist and greasy film irritating his ass and screwing his whole day up. This condition is known as slush butt
by Plazmabat January 11, 2009