| secretly(adverb, clandestine, slyly, underhandedly, surreptitiously) |
| in secret(expression, adverb, unknowing, quietly, secretly) |
| hush-hush(dishonest, secret, private, clandestine, underground) |
| off the record(expression, adjective, idiom, adverb, sensitive) |
| on the sly(expression, adjective, idiom, adverb, secret) |
| undercover(adjective, adverb, dishonest, cunning, deceitful) |
| arcane(obscure, secret, private, unknown, clandestine) |
| backdoor(obscure, sensitive, secret, private, unknown) |
| backstairs(sensitive, mysterious, private, reticent, taciturn) |
| buttoned up(expression, sensitive, reserved, reticent, taciturn) |
| by stealth(expression, clandestine, quietly, secretly, personally) |
| cagey(mysterious, private, reticent, taciturn, covert) |
| clammed up(expression, reserved, mysterious, reticent, taciturn) |
| clandestine(dishonest, cunning, deceitful, secret, private) |
| clandestinely(clandestine, quietly, secretly, personally, privately) |
| classified(obscure, sensitive, secret, private, unknown) |
| close(obscure, reserved, mysterious, private, reticent) |
| close-mouthed(reserved, mysterious, private, reticent, taciturn) |
| concealed(dishonest, cunning, deceitful, secret, hidden) |
| confidential(sensitive, secret, private, hidden, spy) |