Usually refered to as Fucking Cunt; somebodys live-in g/f they can't get rid of for one reason or another that brings everybody down like a wet blanket.
Matt: How's your g/f?
Mike: I don't have a g/f... I have an FC!
Matt: What's an FC?
Mike: A Fucking Cunt
short for Falcon Crust. Which is a condition where by the area around a child's mouth has food all over it. Usually it will have many layers, forming the crust. Play on words from the soap opera Falcon Crest.