Definition from Wiktionary, the free dictionary
Audio (US) (file)
- Plural form of nut
- (vulgar, slang) Testicles.
- Ohhh, he just got kicked in the nuts!
- (poker) A hand that can be proven unbeatable even when the hand's holder does not know any of the hidden cards the other poker players involved in a hand hold or held.
nut — see nut
- (colloquial) Insane, mad.
- After living on the island alone for five years, he eventually went nuts.
- (colloquial, figuratively) Crazy, mad; unusually pleased or, alternatively, angered.
- I just go nuts over her fantastic desserts.
- The referee made a bad call against the home team and the crowd went nuts.
- Indicates annoyance, anger, or disappointment.
- Nuts! They didn't even listen to what I had to say.
- Signifies rejection of a proposal or idea, as in forget it, no way, or nothing doing.
Usage notes 
- The association with testicles (See noun above.) adds an intensifying effect to the anger or rejection.
- Use of "Nuts" rather than another form of "No" is often intentionally insulting.
- Third-person singular simple present indicative form of nut.