1. a person who is tough, stubborn, or difficult to deal with; someone resistant to change or persuasion
Usage: informal; often used with a tone of mild criticism or exasperation
2. a person who is tough or hardened, especially through experience or lifestyle; a seasoned or cynical individual
Usage: informal; sometimes carries a connotation of toughness or world-weariness

Examples

• He's a real hardcase—you won't convince him to change his mind easily.
• The coach said the new recruit was a hardcase who needed discipline.
• She's been through so much that she's become a hardcase about trusting people.
• Don't bother arguing with him; he's a hardcase when it comes to politics.
• The detective had seen enough crime to become a hardcase about human nature.
• My grandfather is a hardcase who refuses to use a smartphone.