When there is too much ketchup in those little paper cups so when you dip anything larger than a french fry the ketchup erupts over the edge onto the table.
Fred tried to dip his burger into the little cup and caused a ketchupcano over the table.
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.