Definition
Nut (UK slang): - Noun: head; a foolish/crazy person; testicle (vulgar) - Verb: to headbutt
Examples
"Use your nut, you daft nut—just square it to the striker!"
"He got clattered in the nuts during five-a-side and went down like a sack of spuds."
"He nutted the bloke outside the pub and got nicked for it."