The infamous battlcry of The Tick, invented by said super hero in order to battle The Terror and his band of super villains.(including Starlings look-a-like)
"And to you evil doers out thier, I say this... KNock off all that evil! Spoooooooooooon!!!!"
~The Tick
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.