One of the more horrific items of practical jokery, basically a "liquid filled" used condom thrown at a (soon to be former) friend or preferably an enemy as you would a water balloon. Not Recommended if you want to remain popular, or indeed, alive.
"Well your honour, I stabbed him 40 times as the previous day he got me in the face with a particularly well filled spunkbomb, covering my skin my clothes, and possibly my soul, with foul salty seminal fluid"
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.