arcane cabalistic censored classified close closed concealed cryptic dark echoless enigmatic esoteric hermetic hidden hush as death hush-hush hushed implicit implied inaudible inferred latent mousy mysterious noiseless occult quiescent quiet restricted secret silent smothered soundless stifled still still as death stilly subaudible suppressed tacit top secret ulterior unarticulated unbreatheable undeclared under security under wraps understood undisclosable undisclosed undivulgable undivulged unexpressed unhearable unmentioned unproclaimed unpronounced unpublished unrecorded unrevealable unrevealed unsaid unsounded unspoken unsung untalked-of untellable untold unutterable unvocalized unvoiced unwhisperable unwritten whist wordless