When you're banging a tranny in the butt when she is lying down. You're so into it that you don't see her jacking one off and she nuts on your Dick causing Cock Stained Balls.
Last night I was doing slippery Sally hard in the ass, right? All of a sudden she busts a nut right on my balls. Fuckin' cock stained balls, man...
It is said of the situation where a person has the bad luck to make contact with his testicles against an undefined surface or object, intentioned or not.
Given the nature of the word, it is more appropriate to design cases where the interaction is made with a moving object, for example, a ball.
Although it is extremely painful for the victim, it tends to be considerably funny to people who witness it.
Today in the baseball game the pitcher took a nutshot; the baseball hit him in the nuts.
Man, I just watched the funniest nutshot video ever.