nut

remove the nut and lubricate the thread.

It is a hard nut for him to crack.

He's a hard nut to crack.

nuts can be eaten in moderation.

the nuts and bolts of public policy.

I was nuts about him.

put a sprinkle of nuts on the cake

Painting the closet was a tough nut to crack.

I'm nuts about opera.

I have a nut to crack with you.

You must be off your nut!

He is nuts about football.

Cashew nuts are rich in carbohydrate.

a local hard nut awaiting trial for murder.

check to ensure that all nuts and bolts are secure.

check that the pipe end and compression nut are not bent out of shape.

technically, a nut is a single-seeded fruit.