| inflexible(adjective, mean, hard, firm, determined) |
| insensible(adjective, bad, cold, aloof, no feelings) |
| insensitive(adjective, bad, cold, aloof, no feelings) |
| rigid(adjective, mean, hard, firm, determined) |
| steely(adjective, firm, solid, determined, stiff) |
| stiffen(verb, dull, close, set, fix) |
| strengthen(verb, dull, close, set, fix) |
| stubborn(adjective, mean, hard, determined, resolute) |
| unbending(adjective, mean, hard, firm, determined) |
| uncompromising(adjective, mean, hard, determined, resolute) |
| unrelenting(adjective, mean, hard, determined, resolute) |
| vitrify(verb, close, set, fix, settle) |
| acclimatize(verb, dull, close, set, develop) |
| calcify(verb, close, set, fix, settle) |
| consolidate(verb, close, set, fix, settle) |
| dry(verb, close, set, fix, settle) |
| fortify(verb, close, set, fix, settle) |
| hard-hearted(adjective, mean, bad, hard, cold) |
| pachydermatous |
| unfeeling(adjective, bad, cold, aloof, no feelings) |