A Bull Shark

If someone jabs you in the back of your head with the knob of their cock, its called a 'Bull Shark'.
You can be 'Bull Sharked' or you can 'Bull Shark' someone.

Ben is such a cunt. The other afternoon, while everyone was waiting to go out, Ben came out of the shower with a semi chubby, snuck up behind Matt and gave him 'A Bull Shark', right on the back of his head. Everyone thought it was hilarious. But Ben's still a cunt.