Standardly used in the sence of a cheating girl or boyfriend when the loyal party walks into a room to find their significant other fucking another. From the point of view of the loyal party all that can be seen from the door looking toward the bed are four legs, two assholes, a pussy (with dick inside), and nuts. The Pussyball kick refers to the action of the loyal party rushing to the bed and kicking or stomping the most vivid region...the pussyball region, injuring both the pussy and nuts of both parties.
I came home from work only to find my girl in bed with another man. I quickly walked to the bed as they were having intercourse and gave a swift pussyball kick before throwing the two of them out of my house in pain.