This is the term used whenever something is done to someone in a harsh manner, whether it is playful or serious. A combination of the words, "got yo ass".
When you dunk on someone... "gotchoass"; When you prove somebodywrong..."gotchoass"; when you trick someone, hit someone, or anything else that excites you and upsets them..."GOTCHOASS"
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.