| perplexing(verb, adjective, hard, obscure, difficult) |
| puzzling(adjective, difficult, strange, mysterious, complicated) |
| confusing(verb, adjective, hard, delicate, loose) |
| mystifying(adjective, obscure, delicate, strange, complex) |
| enigmatic(adjective, hard, obscure, difficult, solid) |
| mysterious(adjective, hard, obscure, delicate, strange) |
| knotty(adjective, hard, tough, difficult, awkward) |
| incomprehensible(adjective, obscure, difficult, solid, strange) |
| bewildering(adjective, hard, delicate, loose, complex) |
| confounding(adjective, hard, delicate, complex, tricky) |
| difficult(adjective, hard, obscure, strange, uncertain) |
| problematic |
| problematical(adjective, hard, delicate, complex, tricky) |
| obscure(adjective, hard, difficult, solid, strange) |
| tough(adjective, difficult, laborious) |
| unfathomable(adjective, hard, obscure, difficult, solid) |
| complex(adjective, hard, difficult, delicate, loose) |
| inexplicable(adjective, hard, obscure, delicate, solid) |
| intricate(adjective, hard, difficult, complex, awkward) |
| cryptic(adjective, obscure, difficult, dark, strange) |