top secret

adjective

Roget 533: secret etc. (concealed) 528; involved &c., 248; labyrinthine, labyrinthian^†, mazy.    confidential; top secret.   

Moby thesaurus: arcane, cabalistic, censored, classified, close, closed, concealed, cryptic, dark, enigmatic, esoteric, hermetic, hidden, hush-hush, latent, mysterious, occult, restricted, secret, smothered, stifled, suppressed, ulterior, unbreatheable, under security, under wraps, undisclosable, undisclosed, undivulgable, undivulged, unrevealable, unrevealed, unspoken, untellable, untold, unutterable, unuttered, unwhisperable ... show more.

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