The action of becoming so angry that one's spine curls into a position where the head can enter the anus. There is a certain nomadic tribe in the frozen deserts of western Mongolia that performs the ancient ritual regularly every Thursday if the weather allows for it.
Guy 1: Bro, I just pissed my dad off so bad that he did a Dr. Cook!
Guy 2: Ok, I'm calling an ambulance right now.
Guy 1: Well shit!