| unsympathetic(adjective, mean, bad, hard, cold) |
| acclimate(verb, dull, close, set, develop) |
| adamant(adjective, mean, hard, tough, resolute) |
| adamantine(adjective, set, firm, determined, stiff) |
| anneal(verb, close, set, fix, settle) |
| fossilize(verb, close, set, fix, settle) |
| hard-boiled(adjective, mean, bad, hard, cold) |
| immovable(adjective, mean, hard, determined, resolute) |
| implacable(adjective, mean, hard, determined, resolute) |
| incompliant(adjective, firm, solid, determined, resolute) |
| inhuman(adjective, bad, cold, aloof, no feelings) |
| intransigent(adjective, determined, resolute, uncompromising, unshakeable) |
| iron(adjective, set, mean, hard, firm) |
| relentless(adjective, mean, hard, determined, resolute) |
| season(verb, dull, close, set, develop) |
| stiff(adjective, set, strong, hard, firm) |
| stiff-necked(adjective, mean, hard, determined, stiff) |
| thick-skinned(adjective, mean, hard, tough, harsh) |
| amalgamate(verb, close, set, fix, settle) |
| bake(verb, close, set, fix, settle) |