The thing you yell when nothing else comes to mind. One of those times when you're so mad that you say something extremely irrelevant and that doesn't even make sense, when you could have just as easily said ass hole.
Tracy: Yeah, thats such a dumb thing to say no one cares.
Sam:Oh.. You...You're such a... a...
Tracy: A what?
Sam: Ass crack!!
Tracy: lol of all the things you could have said...ass hole maybe?.. wow you are just awful.