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