A gesture, Italian in origin, that originally meant "You are dead to me". It has been construed to it's modern day bastardization meaning "Fuck you". However, it is still used in it's original sense by many Italian families.
Mario - *flips his hand from under his chin*
Enzo - What the fuck man? You don't give your boy the fangul.
Mario - You're dead to me, Enzo.