58 entries under idiom topic. ×

16
closed book(noun, expression, trouble, challenge)
7
off the record(expression, adjective, separate, private)
7
under wraps(expression, adjective, adverb, show)
4
mystery story(noun, expression, mystery)
3
not for publication(expression, adjective, sensitive, private)
3
on the sly(expression, private, hidden, sneaky)
3
out of sight
2
behind the scenes(expression, personal, confidential, hush-hush)
2
in secret
1
behind the curtain
1
hush hush
1
in a cloud
1
in a fog
1
in the background(expression, obscure, remote, faraway)
1
in the boonies(expression, obscure, remote, faraway)
1
in the distance(expression, obscure, remote, faraway)
1
in the sticks(expression, obscure, remote, faraway)
1
in the wings
1
middle of nowhere(expression, obscure, remote, faraway)
1
mystery of mysteries
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APASmart Define. (2016). secret thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/secret/thesaurus/synonyms
ChicagoSmart Define. 2016. "secret thesaurus" https://smartdefine.org/secret/thesaurus/synonyms (accessed September 26, 2026).
HarvardSmart Define 2016, secret thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/secret/thesaurus/synonyms>.
MLASmart Define. "secret thesaurus" 31 March 2016. Web. 26 September 2026. <https://smartdefine.org/secret/thesaurus/synonyms>