one's lips are sealed
tip one's hand
let the cat out of the bag
keep quiet
keep one's lips sealed
concealing
concealment
hiding
under wraps
hush up
keep
backroom
confidence
murder will out
cryptadia
pseudosecret
mum's the word
closet
stall
in secret
hidness
underhand
secretly
on the Q.T.
ultrasecret
occulted
keep to oneself
on the QT
tick a lock
exposure
darkness
keep shtum
keep a lid on
semisecret
silence
closeness
keep from
hideling
secretiveness
confidentiality
secrecy
sing like a bird
clandescent
openness
make known
yield up
Deep Throat
unsecrecy
tomb
keep one's counsel
something nasty in the woodshed
top secret
nonsecrecy
steganography
ulterior
give away
divulgation
subterranean
subterraneous
secernent
out
undisclosed
spill the beans
purdah
closehanded
semisecretly
occult
holocryptic
under the covers
undisclosing
on the down-low
covert
transpire
secretive
secret of Polichinelle
hush-hush
closehandedness
conceal
underhanded
telling
keep one's mouth shut
live a lie
nonsecretion
revealing
shoot off at the mouth
telltale
under the table
top-secret
crypto-
out with it
mum
leak out
clammish