best-kept secret
Something interesting or important but not well-known.
Forget the Great Wall - Beijing's best-kept secret is its crazy taxi drivers.
VERBS
be | remain, stay | keep sth
ADV
highly, top, very
The government kept the new defense project highly secret for several years.
absolutely, entirely | more or less
formerly, hitherto, previously
The government finally released documents that were formerly secret to the public.
PREP
from
He didn't want to hide his new job secret from his parents any longer.
ADJ
big, great | little
closely guarded, well-kept
My grandmother's recipe for chocolate cake was a closely guarded secret that she never shared with anyone.
hidden, inner, innermost, intimate
She finally shared her hidden secrets with her best friend after years of keeping quiet.
open
Everyone in the office knew about the manager's plan, though it remained an open secret until the announcement.
dark, guilty, shameful, terrible | commercial, family, military, official, state, trade
VERB + SECRET
have
guard, keep
My best friend has guarded my deepest secret for over ten years.
betray, divulge, let sb in on/into, reveal, tell sb
My best friend finally revealed her secret that she was moving to another country.
find out, uncover
SECRET + VERB
be/get out
If my surprise party plans get out before Friday, the whole thing will be ruined.
PREP
in ~
They decided to have their wedding ceremony in secret because they wanted privacy from the media.
~ about
The family kept a dark secret about what happened to their old house.
~ from
She kept nothing secret from her best friend throughout their entire friendship.
PHRASES
make no secret of the fact that, make a secret of sth
She made no secret of the fact that she wanted to leave her job.
VERB + SECRET
reveal, tell sb
PREP
~ behind
The old detective finally discovered the secret behind the mysterious disappearance.
~ of
She finally discovered the secret of making perfect chocolate chip cookies.
PHRASES
the secret of (sb's) success