hush-hush
hugger-mugger
darkness
underhand
mum
under one's hat
closehandedness
down low
hidness
clandescent
semisecrecy
hole-and-corner
hypersecrecy
confidentiality
spying
cloakedly
clandestine operation
backstage
in secret
secretively
secretly
on the QT
on the Q.T.
secernent
ultrasecret
dark
semisecret
spy
under the table
snooping
closehanded
hypersecretory
covertness
private
confidentialised
pent
hiddenness
secretive
furtive
shoot off at the mouth
industrial espionage
espionage
sensitive
semisecretly
confidentially
secrecy
backroom
leak
news leak
a man's home is his castle
let the cat out of the bag
covert
talk
blab out
subterranean
spill the beans
sing
babble out
peach
blab
closeness
babble
tattle
doc drop
sanctum sanctorum
sanctum
tradecraft
off the grid
under the covers
confidence
on the down-low
secret service
on the hush
shut one's mouth
sub rosa
inside information
keep quiet
exposure
keep one's mouth shut
details
obvelation
talebearing
tattling
blabbermouthed
closemouthed
hidingly
leaky
occulted
tightlipped
under wraps
closelipped
close
deprivatize
delitescency
esoteric