| immaterial(adjective, abstract, theoretical, abstruse, philosophical) |
| impalpable(adjective, abstract, theoretical, abstruse, philosophical) |
| impenetrable(adjective, obscure, dark, superior, mysterious) |
| incorporeal(adjective, abstract, theoretical, abstruse, philosophical) |
| insubstantial(adjective, abstract, theoretical, abstruse, philosophical) |
| intangible(adjective, abstract, theoretical, abstruse, philosophical) |
| intellectual(adjective, abstract, theoretical, abstruse, philosophical) |
| invisible(adjective, obscure, dark, superior, mysterious) |
| jesuitic(adjective, abstract, theoretical, abstruse, philosophical) |
| legendary(adjective, obscure, dark, superior, mysterious) |
| mythical(adjective, obscure, dark, superior, mysterious) |
| mythological(adjective, obscure, dark, superior, mysterious) |
| nonmaterial(adjective, abstract, theoretical, abstruse, philosophical) |
| nonphysical(adjective, abstract, theoretical, abstruse, philosophical) |
| obscure(adjective, dark, superior, mysterious, supernatural) |
| otherworldly |
| oversubtle(adjective, abstract, theoretical, abstruse, philosophical) |
| paranormal(adjective, obscure, dark, mysterious, supernatural) |
| phantom(adjective, obscure, dark, superior, supernatural) |
| phenomenal(adjective, obscure, dark, superior, strange) |