Failure to perform tongue-action between a woman's legs after agreeing to do so as part of a contract.
A lot of guys want to "do it" just with their hoo-haws, so whenever there is an offer to perform cunnilingus as "payment" for said "ultimate favor", perhaps the gal should always half-expect a derelicktion of duty to occur!
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.