-Ass is the suffix you add onto the end of a verb to emphasize the verb itself. It is a commonly used American slang term.
Guy #1: "Hey you wanna come see Twilight with me this weekend?"
Guy #2: "No way, I'm not going to see some corny-ass vampire movie!"
Guy #1: "Hey check out that girl over there."
Guy #2: "Damn, that is one fine-ass chick!"