The act of placing one's posterior against that of another and farting, thus safely depositing the fart in the recipient for later retrieval.
Deav asked his brother at the Indians game, "If you fart into someone's butt, what would you call that?" A guy in the row behind responded, "Well I'd call it a safety deposit box."
Deaver: "I gotta fart!"
Neil: "Quick, stand up and use the safety deposit box!"
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.