implicit
inexplicit
arcane
cabalistic
censored
classified
close
closed
concealed
cryptic
dark
echoless
enigmatic
esoteric
hermetic
hidden
hush as death
hush-hush
hushed
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
darkness
divinely-inspired
half-audible
half-formed
half-stifled
half-uttered
heartfelt
ill-suppressed
inarticulate
inextinguishable
long-drawn-out
milk-punch
often-repeated
ululating
unbranded
unexpressed
unfulfilled
ungratified
unquenchable
unspoken
unworded