62 entries under secret topic. ×

14
surreptitious(adjective, dishonest, hidden, spy)
13
clandestine(adjective, adverb, show, dishonest)
12
covert(adjective, show, reticent, hidden)
11
hush-hush(adjective, adverb, show, informal, dishonest)
11
underground(adjective, unknown, hidden, spy)
9
furtive(adjective, dishonest, reticent, hidden)
8
hidden(adjective, spy, clandestine, underground)
8
hole-and-corner(adjective, private, hidden, spy)
7
confidential(adjective, hidden, spy, clandestine)
7
private(adjective, unknown, hidden, spy)
7
stealthy(adjective, quiet, dishonest, hidden)
7
underhand(adjective, deceitful, hidden, spy)
6
concealed(adjective, obscure, dishonest, hidden)
6
under wraps(expression, adjective, idiom, show, dishonest)
6
secluded(adjective, unknown, hidden, underground)
5
cloak-and-dagger(adjective, show, full, sly)
5
spy(adjective, warning, hidden, covert)
4
occult(unknown, hidden, underground, concealed)
4
underhanded(dishonest, cunning, deceitful, hidden)
3
buried(adjective, unknown, hidden, concealed)
11 years ago|6.9k views|share |citing 
APASmart Define. (2015). undercover thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/undercover/thesaurus/synonyms
ChicagoSmart Define. 2015. "undercover thesaurus" https://smartdefine.org/undercover/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2015, undercover thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/undercover/thesaurus/synonyms>.
MLASmart Define. "undercover thesaurus" 13 April 2015. Web. 27 September 2026. <https://smartdefine.org/undercover/thesaurus/synonyms>