| mysterious(clandestine, underground, undisclosed) |
| mystic(clandestine, underground, undisclosed) |
| mystical(clandestine, underground, undisclosed) |
| noiseless(adjective, silent, sneak, skulking) |
| not for publication(expression, adjective, idiom, sensitive) |
| not true to(expression, idiom, fickle, untrustworthy, unprincipled) |
| obscure(clandestine, underground, undisclosed) |
| obscured(secret, hidden, covert) |
| occult(clandestine, underground, undisclosed) |
| of bad faith(expression, idiom, fickle, untrustworthy, unprincipled) |
| out-of-the-way(clandestine, underground, undisclosed) |
| perfidious(fickle, untrustworthy, unprincipled, dirty-dealing) |
| perjurious(fickle, untrustworthy, unprincipled, dirty-dealing) |
| polygamous(fickle, untrustworthy, unprincipled) |
| privately(adverb, secretly, furtively) |
| privileged(adjective, sensitive) |
| quicksilver(fickle, untrustworthy, unprincipled, dirty-dealing) |
| recondite(clandestine, underground, undisclosed) |
| reticent(clandestine, underground, undisclosed) |
| retired(clandestine, underground, undisclosed) |