keep
keep quiet
keep to oneself
hush up
shut one's mouth
keep one's mouth shut
keep one's lips sealed
give away
disembosom
secretly
on the Q.T.
on the QT
in secret
breast one's cards
secrecy
keep a lid on
undisclosedly
let the cat out of the bag
revealing
telling
oversecrete
telltale
keep from
secret
mum's the word
keep shtum
darkness
confidentiality
silence
secretiveness
steal
cryptadia
confide
between you and me
restrict
secretive
unsecretly
secernent
semisecret
unmuffle
evasive
sensitive
under wraps
make known
undisclosed
keep mum
closet
concealing
keep one's counsel
concealment
conceal
privily
hiding
ulterior
straightforward
stifle
aboveboard
confidable
transpire
disguise
stall
subterranean
subterraneous
semisecretly
sing like a bird
giveaway
secretively
one's lips are sealed
hypersecrete
cloakedly
undisclosing
superarcane
hypersecrecy
babble
self-edit
under the radar
closehandedness
hiddle
confidence
confidentially
hidness
betray
something nasty in the woodshed
underhanded
sub rosa
under one's hat
relieve
hiss-and-tell
unbosom
leak
hugger-mugger
secretness
mum
tick a lock