Short form of "what". Is usually used by people who's synapses fire at a very slow rate. Can be used by otherwise literate people to convey a state of being utterly flabbergasted.
Nick: So, your cousin is sleeping over tonight.
Nick: Is that your cousin in the picture on your Myspace?
Nick: She looks pretty cool.
George: Sure, she's cool.
Nick: She's hot, actually.
Nick: Can I sleep over tonight?