When two people are engaged in sex, one person, usually the male, inserts their finger in the anal cavity of their partner, and proceeds to wipe particles of feces on the upper lip of their mate.
My girlfriend and I were having sex last night, and right after I had an orgasm I gave her a dirty sanchez.
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.