Person in the world of the show Avatar: The Last Airbender who has the power to manipulate/generate fire and sometimes lightning. It is based upon Northen Shaolin and several other styles of Kung Fu.
A firebender could kick your face in AND turn you into a smoldering pile of ashes.
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.