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