calling dibs is a slang term that refers to a male "claiming" the rights to pursue a woman. dibs can be called in either a serious or a sarcastic fashion as long as all males in the party are aware of the context.
A group of (male) friends is at a party to check out some girls. Whoever spots a pretty girl first can "call dibs" on her. That way he can make sure none of his buddies would make a movie on her.
