| resist(adjective, strain, firmness, labour, hardiness) |
| rock-solid(adjective, strain, firmness, compact, dense) |
| toilsome(adjective, great, tough, difficulty, difficult) |
| well-established(adjective, strain, firmness, labour, hardiness) |
| rugged(adjective, strong, tough, severe, continue) |
| complicated(adjective, difficult, property, complex, awkward) |
| grievous(adjective, tough, severe, rough, difficult) |
| intricate(adjective, difficult, property, complex, awkward) |
| operose(adjective, tough, severe, difficulty, rough) |
| oppressive(adjective, dull, tough, severe, rough) |
| thorny(adjective, rough, difficult, delicate, complex) |
| trying(adjective, dull, tough, severe, rough) |
| knotty(adjective, severe, rough, difficult, violent) |
| painful(adjective, evil, rough, nasty, difficult) |
| taxing(adjective, tough, severe, rough, difficult) |
| stern(adjective, person, mean, tough, easy) |
| unsympathetic(adjective, person, mean, cool, tough) |
| backbreaking(adjective, difficult, heavy, complex, awkward) |
| punishing(adjective, difficult, complex) |
| solid(adjective, adverb, characteristic, person, body) |