When a man thrusts into another man, and that power carries through into the next man, and then the next. It goes down the chain until there is no power from the initial thrust.
Those 4 guys got in a line butt booty naked, and they form a Newton's Cradle of guys fucking. They participated in a Tasmanian Bull Fuck!
a sexual position only done by professionals where as the girl back bends onto the while the boy is sitting, and thrusting inside of her. a very complex position.
Guy 1: hey do you know kim? she gave me a green-eyed-bull
Guy 2: what really? your kidding.