| incomprehensible(adjective, knowledge, solid, dark, strange) |
| enigmatic(adjective, obscure, strange, blank, sophisticated) |
| mysterious(adjective, dark, strange, uncertain, secret) |
| unfathomable(adjective, knowledge, obscure, dark, strange) |
| cryptic(adjective, obscure, dark, sophisticated, mysterious) |
| puzzling(adjective, obscure, dark, strange, sophisticated) |
| impenetrable(adjective, knowledge, obscure, blank, sophisticated) |
| inexplicable(adjective, solid, dark, uncertain, blank) |
| dark(adjective, obscure, mysterious, feature, hidden) |
| obscure(adjective, dark, strange, sophisticated, mysterious) |
| unintelligible(adjective, knowledge, solid, dark, strange) |
| arcane(adjective, solid, strange, blank, dense) |
| deep |
| mystic(adjective, solid, strange, blank, secret) |
| difficult(adjective, strange, blank, hidden, complicated) |
| mystifying |
| occult(adjective, dark, strange, uncertain, odd) |
| unaccountable(adjective, solid, strange, blank, dense) |
| unexplainable(adjective, strange, blank, hidden, unfathomable) |
| abstruse(adjective, obscure, strange, sophisticated, supernatural) |