| unknown(adjective, obscure, strange, mysterious, indefinite) |
| unexplained(adjective, strange, new, remote, mysterious) |
| mysterious(adjective, strange, new, remote, indefinite) |
| strange(adjective, new, remote, mysterious, indefinite) |
| uncharted(adjective, strange, new, remote, mysterious) |
| unconfirmed |
| undiscovered(adjective, strange, new, remote, mysterious) |
| unexplored(adjective, strange, new, remote, mysterious) |
| unfamiliar(adjective, strange, new, remote, mysterious) |
| unidentified(adjective, strange, new, remote, mysterious) |
| able |
| unapprehended(adjective, strange, new, remote, mysterious) |
| unauthenticated |
| undemonstrated |
| undetermined(strange, indefinite, unidentified) |
| unheard-of(strange, new, remote, indefinite, unidentified) |
| unperceived(strange, new, remote, mysterious, indefinite) |
| unrevealed(strange, new, remote, mysterious, indefinite) |
| X(strange, new, remote, mysterious, indefinite) |
| alien(strange, new, remote, mysterious, indefinite) |