| exacting(adjective, hard, tough, severe, rough) |
| fancy(adjective, hard, difficult, exact, complex) |
| fussy(adjective, fancy, difficult, exact, complex) |
| inscrutable |
| intractable(difficulty, problematic) |
| knurly |
| labyrinthian |
| mean(adjective, hard, tough, severe, rough) |
| mysterious(adjective, hard, evil, delicate, loose) |
| nettlesome(tough, tricky, complicated, problematic, thorny) |
| nodular(adjective, harsh, coarse, irregular, uneven) |
| paradoxical(adjective, hard, obscure, sophisticated, tricky) |
| rigorous(adjective, tough, severe, rough, difficult) |
| rococo(adjective, complex, involved, complicated) |
| secret(adjective, evil, deep, mysterious, hidden) |
| slavish(adjective, tough, rough, difficult, heavy) |
| spiny(tricky, complicated, thorny, spiky) |
| touchy(delicate, awkward, complicated) |
| twisting |
| twisty |