| stiff(adjective, feature, state, characteristic, strong) |
| firm(noun, adjective, feature, state, characteristic) |
| inflexible(adjective, mean, strong, hard, tough) |
| unyielding(adjective, mean, strong, hard, tough) |
| stubborn(adjective, characteristic, quality, mean, strong) |
| uncompromising(adjective, mean, hard, tough, severe) |
| hard(adjective, feature, state, characteristic, mean) |
| obdurate(adjective, strong, hard, tough, severe) |
| unbending(adjective, mean, strong, hard, tough) |
| persistent(adjective, feature, state, characteristic, severe) |
| intransigent(adjective, tough, severe, resist, determined) |
| determined(adjective, strong, hard, tough, severe) |
| inexorable(adjective, mean, strong, hard, tough) |
| resolute(adjective, tough, severe, firm, harsh) |
| immovable(adjective, mean, strong, hard, secure) |
| set(verb, adjective, hard, secure, tough) |
| unrelenting(adjective, mean, strong, hard, tough) |
| relentless(adjective, mean, strong, hard, tough) |
| fixed(adjective, mean, hard, complete, secure) |
| steadfast(adjective, feature, state, characteristic, secure) |