What does the it mean when someone says that a person is a hard nut to crack?
A person that is a hard nut to crack refers to someone who is difficult to deal with, or a person who is difficult to know, understand or convince of something.
When someone says that a person is a hard nut to crack they are saying that the person is stubborn. It means that a person sticks to what they believe to be right.
it means that you can't get over that person quickly
It means hard to know what motivates them and a reluctance to allow any one get close enough to find out.