| hard-boiled(adjective, hard, careless, indifferent, cruel) |
| hard as nails(expression, adjective, idiom, set, strong) |
| hornified |
| impenetrable(adjective, set, hard, firm, stiff) |
| impenitent(adjective, hard, careless, indifferent, cruel) |
| impervious |
| impious(adjective, hard, unfeeling, unsympathetic, hardened) |
| inaccessible(adjective, hard, unfeeling, unsympathetic, hardened) |
| incrusted |
| indifferent(adjective, hard, cool, careless, cruel) |
| inexcitable(adjective, cool, blank, aloof, unemotional) |
| inexpressive(adjective, cool, blank, aloof, unemotional) |
| inscrutable(adjective, cool, blank, aloof, unemotional) |
| insensate(adjective, hard, careless, indifferent, cruel) |
| insentient(adjective, hard, careless, indifferent, cruel) |
| insusceptible(adjective, cool, blank, aloof, unemotional) |
| irreverent(adjective, hard, unfeeling, unsympathetic, hardened) |
| lapidified |
| lost to shame(expression, idiom) |
| matter-of-fact(adjective, cool, blank, aloof, unemotional) |