DAILY UPDATED VOCABULARY WITH PICTURES.

• nut [countable]
• 1

  food

  a dry brown fruit inside a hard shell, that grows on a tree:
• a pine nut
• roasted nuts
• We were sitting round the fire cracking nuts (=opening them).
• 
  
• 2

  tool

  a small piece of metal with a hole through the middle which is screwed onto a bolt to fasten things together:
• Use a wrench to loosen the nut.
• 3

  crazy person

  informal someone who is crazy or behaves strangely:
• My dad is such a nut.
• What are you, some kind of nut?
• 4

   golf/opera etc nut

  informal someone who is very interested in golf etc[↪ fanatic]:
• You don't have to be a sports nut to enjoy skiing.
• 5

  sex organ

   nuts

   [plural] informal a man's testicles
• 6

   the nuts and bolts of something

  informal the practical details of a subject or job:
• the nuts and bolts of government
• 7

   tough/hard nut

  informal someone who is difficult to deal with:
• He may have softened a bit in his old age but he's still a tough nut.
• 8

   a hard/tough nut to crack

  a difficult problem or situation:
• Celtic have lost only once this season and will be a tough nut to crack.
• 9

   be off your nut

  British English spoken informal to be crazy:
• You must be off your nut!
• 10

   do your nut

  British English spoken to become very angry or worried:
• I didn't get home till three - my mum did her nut!
• 11

  head

  British English spoken old-fashioned your head or brain
• somebody's nut
• Oh come on, use your nut!

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.