| unintelligible(adjective, knowledge, obscure, difficult, solid) |
| unfathomable(adjective, hard, knowledge, obscure, difficult) |
| obscure(adjective, difficult, solid, dark, strange) |
| puzzling(adjective, obscure, dark, strange, mysterious) |
| mysterious(adjective, obscure, dark, strange, secret) |
| inscrutable(adjective, knowledge, solid, dark, strange) |
| enigmatic(adjective, obscure, difficult, solid, strange) |
| inexplicable(adjective, obscure, solid, dark, strange) |
| impenetrable(adjective, knowledge, obscure, solid, dark) |
| cryptic(adjective, obscure, difficult, dark, strange) |
| dark(adjective, mysterious, feature, obscure, hidden) |
| perplexing(adjective, obscure, difficult, dark, strange) |
| abstruse(adjective, obscure, difficult, strange, uncertain) |
| baffling(adjective, obscure, difficult, solid, strange) |
| recondite(adjective, obscure, dark, strange, uncertain) |
| arcane(adjective, obscure, difficult, solid, strange) |
| inconceivable(adjective, belief, understandable) |
| mystifying(adjective, understandable) |
| unclear(adjective, obscure, difficult, uncertain, doubtful) |
| indecipherable(adjective, dark, uncertain, deep, mysterious) |