keep quiet
• refrain from speaking or from disclosing something secret.
keep something quiet
• refrain from disclosing information about something; keep something secret.
Similar:
secret,
top secret,
confidential,
strictly confidential,
classified,
unrevealed,
undisclosed,
unpublished,
untold,
unknown,
uncommunicated,
under wraps,
unofficial,
off the record,
not to be made public,
not to be disclosed,
clandestine,
surreptitious,
sub rosa,
hush-hush,
mum,
