1. A nap at an awkward time of day or night which leaves one feeling much worse than before the nap.
2. A nap that leaves one feeling cracked out.
"I accidentially fell asleep at 7:00 last night, and when I woke up from my crack-nap at 9:30, I felt shitty so didn't know if I should eat soomething or just go back to sleep."
A cracknappa is a person who has no abilities in any fields and is completely and utterly useless. This person will more often than not be a noob also.
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.