clammish
nonconcealment
incommunicative
something nasty in the woodshed
supersecret
covert
closemouthed
secernent
occult
hidness
giveaway
secrecy
secret
sub rosa
secretiveness
backroom
in secret
on the Q.T.
secretly
on the QT
uncandid
underground
qabalistic
privacy
privateness
sibylline
silence
hideling
ulterior
subterranean
kabbalistic
closeness
cryptic
subterraneous
cabalistic
cryptical
hide-all
concealment
incommunicable
uncommunicativeness
holocryptic
submarine
semisecret
stealth
under the table
closehanded
underhanded
divulgence
divulgement
under one's hat