There's these two nuns driving in a car when all of a sudden the devil lands on top of there bonnet. The nun driving says to the other "oh no, what should we do?" The other nun say's "show him your cross" So she sticks her head out the window and say's "GET OFF OF MY CAR YOU F***ING C**T!"
Sorry to make me sound dumb...I don't get it at all...
Well if your like me the first time I heard it I thought the nun was going to show the devil a cross, like a cross that you would wear around you're neck. BUT.... the joke is when she starts swearing at the devil to get off her car because cross also means to be angry.