| impenetrable(adjective, obscure, solid, dark, superior) |
| mysterious(adjective, solid, strange, secret, dense) |
| unfathomable(adjective, hard, obscure, difficult, solid) |
| unintelligible(adjective, obscure, solid, dark, superior) |
| incomprehensible(adjective, obscure, solid, dark, strange) |
| incognizable(adjective, solid, deep, dense, unfathomable) |
| inconceivable(adjective, obscure, extraordinary, belief, fantastic) |
| inscrutable(adjective, solid, strange, blank, dense) |
| unknown(adjective, obscure, dark, superior, strange) |
| arcane(adjective, solid, strange, odd, mysterious) |
| enigmatic(adjective, obscure, solid, strange, odd) |
| hidden(adjective, obscure, solid, dark, superior) |
| strange(adjective, extraordinary, unbelievable, implausible, unfathomable) |
| undiscoverable(adjective, difficult, ambiguous, hidden, unfathomable) |
| unimaginable(adjective, extraordinary, strange, implausible, unfathomable) |
| inexplicable(adjective, obscure, solid, dark, strange) |
| mystic(adjective, obscure, solid, dark, superior) |
| obscure(adjective, solid, dark, mysterious, unfathomable) |
| transcendent |
| unaccountable(adjective, solid, strange, mysterious, secret) |