| refractory(adjective, strain, firm, solid, firmness) |
| stationary(adjective, strain, firmness, labour, hardiness) |
| substantial(adjective, close, strong, hard, strain) |
| abundant(adjective, strain, firmness, labour, hardiness) |
| constant(adjective, strain, firmness, labour, hardiness) |
| hard-nosed(adjective, hard, severe, difficult, complex) |
| hefty(adjective, hard, difficult, complex, compact) |
| immune(adjective, strain, firmness, safe, unaffected) |
| inextricable(adjective, hard, difficult, complex) |
| resilient(adjective, strong, strain, stiff, firmness) |
| robust(adjective, strain, firmness, labour, hardiness) |
| rock-solid(adjective, hard, strain, firmness, compact) |
| stout(adjective, strain, firmness, labour, hardiness) |
| tolerant(adjective, strain, firmness, labour, hardiness) |
| withstanding(adjective, strong, strain, stiff, firmness) |
| frugal(adjective, characteristic, quality, poor, small) |
| narrow(adjective, close, poor, informal, small) |
| mingy(adjective, prudent, selfish, stingy, sparing) |
| secure(verb, adjective, close, set, strong) |
| lit(adjective, state, characteristic, quality, slang) |