| hard(strong, tough, sturdy, rigid, rugged) |
| hard-boiled(strong, hard, tough, sturdy, rugged) |
| hard-core(strong, hard, tough, sturdy, rugged) |
| hard-line(strong, hard, tough, sturdy, rugged) |
| hard-nosed(strong, hard, tough, sturdy, rugged) |
| hard-shell(strong, hard, tough, sturdy, rugged) |
| hard as nails(expression, idiom, strong, hard, tough) |
| hardheaded(strong, hard, tough, sturdy, rugged) |
| harsh(strong, hard, tough, sturdy, rugged) |
| heavy(strong, hard, tough, sturdy, rigid) |
| immovable(strong, hard, tough, sturdy, rigid) |
| implacable(strong, hard, tough, sturdy, rigid) |
| indomitable(strong, hard, tough, sturdy, rigid) |
| inexorable(strong, hard, tough, sturdy, rigid) |
| inflexible(strong, hard, tough, sturdy, rugged) |
| insensible(strong, hard, tough, sturdy, rigid) |
| iron(strong, hard, tough) |
| mortified(strong, hard, tough, sturdy, rugged) |
| mulish(strong, hard, tough, sturdy, rugged) |
| obdurate(strong, hard, tough, sturdy, rigid) |