"Venom bites" refer to the piercing of the tongue with two barbells, side-by-side. Some piercers refuse to do this type of tongue piercing due to the risk of puncturing one of the major veins in the tongue. They are not a lip piercing, contrary to what some believe.
guy 1: I bet that girl Jessica gives good dome. Did you see her venom bites?
guy 2: Hell yeah, she seems like a real freak too.