Quite often is mistakened for phone "sex" but in actuality, it is just simply conversing on the telephone. However, it is more appropiately used with the opposite sex. boyfriend/girlfriend type of deal, or vice versa.
"Me and my girl were phone banging until midnight before she got sleepy and went to bed."
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.