Its when youre three days out from your last nut shave, and the stubble causes a rash on your partners chin and ass cheeks.
Beth: Maggie, what happned to your face?
Maggie: That goddamn Chuck has a bad case of stubble nuts, it's killin me!
Beth: Lets go buy him some edge gel or somthin'!
When you nut so hard that you stumble and almost fall over. Causing someone to stumblenut can be a point of pride.
Dave: Lauren sucked me off so good last night that I almost fell over!
Robert: Damn, she made you stumblenut? That's lit, I haven't had a succ that good since my ex left me!