| hardhearted(adjective, hard, indifferent, unfeeling, unkind) |
| healthy(adjective, strong, hard, solid, heavy) |
| heartless(adjective, feeling, hard, cold, indifferent) |
| heavy(adjective, strong, hard, sound, tough) |
| heavy-duty(adjective, strong, sound, tough, solid) |
| hefty |
| hold the fort(expression, adjective, idiom, tough, firm) |
| hold the line(expression, adjective, idiom, tough, firm) |
| husky |
| immovable(adjective, calm, strong, hard, cool) |
| impenetrable(adjective, set, strong, hard, firm) |
| imperceptive(adjective, hard, indifferent, unkind, unresponsive) |
| imperturbable(adjective, calm, cool, collected, unflappable) |
| in fine feather(expression, adjective, idiom, strong, sound) |
| incompliant(adjective, tough, firm, fixed, distant) |
| incurious(adjective, hard, indifferent, unkind, unresponsive) |
| indurated(adjective, set, strong, hard, unfeeling) |
| inelastic(adjective, tough, firm, fixed, distant) |
| inexorable(adjective, strong, hard, tough, firm) |
| inflexible(adjective, set, strong, hard, tough) |