1. Plural of hardcase; people who are tough, stubborn, or difficult to deal with; individuals resistant to change or persuasion.
Usage: informal; often used in a slightly derogatory sense
2. Plural of hardcase; criminals or tough individuals, especially those considered dangerous or hardened.
Usage: slang; informal

Examples

• The coach said the team was full of hardcases who refused to follow the new training regimen.
• Those hardcases in the neighborhood had a reputation for trouble.
• She's one of the hardcases at work—you can't convince her to try anything new.
• The prison housed some of the state's most dangerous hardcases.
• Even the hardcases on the committee eventually agreed to the proposal.