In the rare instance when a man has three testicles the third one is the money ball. It is usually the ball in the middle.
Dude I heard Jim has a money ball!
In a game of foosball, Money Ball occurs when both teams are on game point. At this time, it is customary to cheers, drink, and insult the opposing team and/or teammate.
Team 1: 9pts Team 2: 9pts
Fooser #1 "Money Ball!"
Fooser #2 "Cheers to you losing Boy-O"
Fooser #1 "Cheers to your Mom blowin' me later"