The part of your ballsack right where your buttcrack starts, in between your legs.
Dude, my butt nut is itching soooooo bad!
by rdogvids123 April 11, 2010
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when you fuck your significant other in the ass and do not take a shower the next day.
I railed my old lady in the ass and woke up late so i didn't get a shower now i have butt nuts!
by jeffro7946 March 24, 2009
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When ones ball sack is so big that you can hit them from behind ones butt which cause temporary stinging pain.
When Jack bent over to retrieve his phone, Brook slapped his ass and unknowingly hit his butt nuts.
by Jax in the box May 13, 2011
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