Synonyms and related words :
arcane, cabalistic, censored, classified, close, closed, concealed, cryptic, dark, enigmatic, esoteric, hermetic, hidden, hinted, hush-hush, implicit, implied, inferred, intimated, latent, mute, mysterious, occult, restricted, secret, silent, smothered, stifled, suggested, suppressed, tacit, top secret, ulterior, unbreatheable, undeclared, under security, under wraps, understood, undisclosable, undisclosed, undivulgable, undivulged, unexpressed, unmentioned, unproclaimed, unpronounced, unpublished, unrecorded, unrevealable, unrevealed, unsaid, unstated, unsung, untalked-of, untellable, untold, unutterable, unuttered, unvoiced, unwhisperable, unwritten, wordless