| stubborn(adjective, hard, unfeeling, unsympathetic, hardened) |
| callous(verb, adjective, dull, hard, develop) |
| hardened(verb, adjective, hard, unfeeling, unsympathetic) |
| hard(adjective, unfeeling, unsympathetic, hardened, callous) |
| inflexible(adjective, hard, unfeeling, unsympathetic, hardened) |
| inured(adjective, hard, unfeeling, unsympathetic, hardened) |
| obdurate(adjective, hard, unfeeling, unsympathetic, hardened) |
| thick-skinned(adjective, hard, unfeeling, unsympathetic, hardened) |
| balky |
| brazenfaced |
| caked(verb, adjective, jellied, gel, calcify) |
| calcified(verb, adjective, jellied, gel, calcify) |
| calcify(verb, close, set, firm, dry) |
| case-hardened(verb, adjective, hard, unfeeling, unsympathetic) |
| caseharden(verb, close, set, firm, dry) |
| coldhearted(adjective, hard, unfeeling, unsympathetic, hardened) |
| densify(verb, close, set, firm, dry) |
| fossilize(verb, close, set, firm, dry) |
| hard-nosed(adjective, hard, unfeeling, unsympathetic, hardened) |
| indurate(verb, adjective, dull, develop, blunt) |