| mystical(clandestine, underground, undisclosed) |
| not for publication(expression, adjective, idiom, exceptional, sensitive) |
| obscure(clandestine, underground, undisclosed) |
| off the record(expression, idiom, exceptional, secret, private) |
| on the QT(expression, adjective, idiom, sensitive, private) |
| out-of-the-way(clandestine, underground, undisclosed) |
| privileged(adjective, sensitive, private, confidential, sub-rosa) |
| privy(private, confidential) |
| recondite(clandestine, underground, undisclosed) |
| reticent(clandestine, underground, undisclosed) |
| retired(clandestine, underground, undisclosed) |
| secluded(clandestine, underground, undisclosed) |
| secrecy |
| sensitive(adjective, secret, sub-rosa) |
| shrouded(clandestine, underground, undisclosed) |
| special |
| strange(clandestine, underground, undisclosed) |
| top-secret(secret, clandestine, underground, undisclosed, ranked) |
| under the table(expression, adjective, idiom, close, sensitive) |
| undercover(clandestine, underground, undisclosed) |