tough nut to crack
The definition of tough nut to crack is someone who it is hard to get close to, hard to get to know or hard to understand.
An example of a tough nut to crack is a mysterious friend you have who never really opens up about herself or lets you get close.
(plural tough nuts to crack)
- Used other than as an idiom: see tough, nut, crack.
- (idiomatic) A problem that is challenging to solve.
- (idiomatic, by extension) A situation, person, group, etc. which is difficult to deal with.
- (idiomatic) A place, opportunity, etc. to which it is difficult to gain entry.
- An amount that is difficult to finance.