| classified(noun, adjective, sensitive, secret, restricted) |
| close(inside, clandestine, underground, undisclosed, furtive) |
| hush-hush(noun, adjective, secret, restricted, hidden) |
| secret(adjective, sensitive, private, hidden, clandestine) |
| under wraps(noun, expression, adjective, sensitive, underground) |
| arcane(clandestine, underground, undisclosed) |
| clandestine(underground, undisclosed) |
| cryptic(close, inside, clandestine, underground, undisclosed) |
| esoteric(clandestine, underground, undisclosed) |
| hidden(clandestine, underground, undisclosed) |
| mysterious(clandestine, underground, undisclosed) |
| occult(clandestine, underground, undisclosed) |
| private(secret, clandestine, underground, undisclosed, confidential) |
| restricted(adjective, secret, private, hidden, clandestine) |
| undisclosed(clandestine, underground) |
| unrevealed(clandestine, underground, undisclosed) |
| backdoor(adjective, close, sensitive, inside, clandestine) |
| backstairs(adjective, close, sensitive, inside, clandestine) |
| camouflaged(close, clandestine, underground, undisclosed, furtive) |
| censored |