When your girlfriendsticks her middle finger up you ass while you're sleeping and gives you a mustache with it... Payback fory the good old dirty sanchez!
Woke in the middle of the night to a sharp pain in my ass, didn't know till morning when I went to brush my teeth that my girl had given me a dirty Khristina...
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.