| tricky(adjective, hard, difficult, complex, sophisticated) |
| thorny(adjective, hard, difficult, delicate, loose) |
| convoluted(adjective, hard, fancy, obscure, difficult) |
| covert(strange, secret, unknown, hidden, curious) |
| equivocal(adjective, obscure, difficult, dark, strange) |
| hermetic(obscure, dark, deep, mysterious, secret) |
| indistinct(adjective, uncertain, vague, unclear, unintelligibility) |
| obscured(adjective, hidden, indefinite, unreal, insubstantial) |
| shadowy(adjective, obscure, dark, unknown, hidden) |
| unclear(adjective, hard, obscure, difficult, loose) |
| unknown(obscure, dark, strange, deep, secret) |
| arduous(adjective, hard, fancy, difficult, complex) |
| cabbalistic |
| challenging(adjective, obscure, difficult, inaccessible) |
| close(obscure, dark, secret, unknown, hidden) |
| clouded(obscure, dark, secret, unknown, hidden) |
| covered(obscure, secret, unknown, hidden, concealed) |
| critical(sharp, exact, discriminating) |
| cryptical |
| cultivated(knowledgeable, cultured, educated, erudite, enlightened) |