| refractory(adjective, strain, firmness, labour, hardiness) |
| resistant(adjective, strain, firmness, labour, hardiness) |
| set(verb, adjective, calm, strong, secure) |
| stationary(adjective, move, strain, firmness, labour) |
| stout(adjective, calm, strong, tough, strain) |
| substantial(adjective, calm, strong, secure, strain) |
| unbending(adjective, clear, strong, tough, severe) |
| obstinate(adjective, strong, tough, firm, intense) |
| perpetual(adjective, strain, determined, steady, stable) |
| tight(adjective, strain, firmness, rigid, labour) |
| impregnable(adjective, strain, firmness, labour, hardiness) |
| quiescent(adjective, strain, firmness, labour, hardiness) |
| resolved(adjective, strong, flat, firm, certain) |
| stabile(adjective, calm, strong, secure, strain) |
| sustained(adjective, strain, firmness, persistent, continuous) |
| adamant(adjective, strong, secure, tough, flat) |
| inexorable(adjective, firm, determined, steady, resolute) |
| staying(adjective, strain, firmness, labour, hardiness) |
| true(adjective, good, close, strong, kind) |
| unshakable(adjective, firm, determined, resolute, obstinate) |