The inadvertent exposure of ones testicle or testicles while performing some activity. The male version of the female nip slip.
Look at old man River over on the incline bench with his balls out. Yep, thats a full nut slip.
nut slip: define #2
noun: when ur trying to stick ur nuts inside a girls pink taco and u have one in and u go to stick the other in and the other comes out then u have a nut slip.
jovany was trying to put his nuts in maxines vagina and he had a nut slip…poor dude