| insensitive(adjective, hard, tough, indifferent, cruel) |
| insusceptible(adjective, hard, insensitive, unsusceptible) |
| intractable(adjective, tough, firm, fixed, distant) |
| locked in(expression, adjective, tough, firm, distant) |
| marble |
| marblelike |
| muscular(adjective, strong, sound, tough, solid) |
| nail |
| nerveless(adjective, calm, cool, steady, tranquil) |
| nervy |
| nonchalant(adjective, calm, cool, steady, unaffected) |
| obtuse(adjective, hard, indifferent, unfeeling, unkind) |
| pitiless(adjective, cruel, vicious, fixed, unfeeling) |
| red-blooded |
| reinforced(adjective, strong, sound, tough, solid) |
| relentless(adjective, strong, hard, tough, firm) |
| reserved(adjective, tough, firm, fixed, distant) |
| resolute(adjective, tough, firm, fixed, serious) |
| rigid(adjective, set, strong, hard, tough) |
| roll with punches(expression, adjective, idiom, calm, cool) |