The simultaneous act of shitting, wanking and vomiting. (Legend states that successful completion of this will result in instant teleportation to your home toilet)
Person 1: Did you hear what happened to Dylan?
Person 2: No what happened?
Person 1: He did a Shwank Vombomb!
Person 2: Thats awesome!
When a person is about to take part in coitus, but instead the person follows through with projectile vomiting over both the bed and the partner, and afterwards passes out face down on the floor. Thus leaving the partner covered in vomit and unsatisfied.