It primarily involves a closed fist contacting the soft underbelly of a person (beneath the rib cage) at a high velocity, causing the ensuing force to press upward on the victim's diaphram, leading to a sudden expulsion of air from the victim's mouth and lungs. This opening blow leaves the victim open to various other attacks, often leading to what would be called "bitch moves" becuase of the defenseless nature of the victim.
"Hi CJ. It went swimmingly! I met up with Mona and she suckerpunched me for, like, an hour. My scrot really hurts today. And my wang is all dried up"