A term used exclusively by the female
gender when they want you to
get off their back about something, but it is in fact, that
deep.
Guy: Are you really staying over at Bronte's house? I thought you guys were just coworkers.
Girl: Yeah, we're just friends.
Guy: Uh huh. And I heard he was talking about getting a new
girlfriend and that she was coming over tonight. Are you
sure that's not you?
Girl: It's not that
deep.