49 entries under underhanded topic. ×

14
surreptitious(adjective, dishonest, secret, hidden, spy)
13
clandestine(adjective, adverb, show, dishonest, secret)
13
secret(adjective, quiet, show, dishonest, hidden)
12
covert(adjective, show, secret, reticent, hidden)
11
hush-hush(adjective, adverb, show, informal, dishonest)
9
furtive(adjective, dishonest, secret, reticent, hidden)
7
private(adjective, secret, unknown, hidden, spy)
7
stealthy(adjective, quiet, dishonest, secret, hidden)
6
concealed(adjective, obscure, dishonest, secret, hidden)
3
buried(adjective, secret, unknown, hidden, concealed)
3
sneaking(adjective, dishonest, cunning, deceitful, secret)
3
disguised(adjective, obscure, secret, hidden, clandestine)
3
incognito(adjective, adverb, informal, secret, hidden)
3
obscured(adjective, secret, hidden, underground, concealed)
2
cloaked(obscure, secret, unknown, hidden, clandestine)
2
masked(obscure, secret, unknown, hidden, concealed)
2
on the QT(expression, adjective, idiom, adverb, dishonest)
2
shifty(dishonest, cunning, deceitful, sneaky)
2
shrouded(obscure, secret, unknown, hidden, clandestine)
2
sub-rosa(adjective, dishonest, cunning, deceitful, secret)
<123>
11 years ago|6.9k views|share |citing 
APASmart Define. (2015). undercover thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/undercover/thesaurus/synonyms
ChicagoSmart Define. 2015. "undercover thesaurus" https://smartdefine.org/undercover/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, undercover thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/undercover/thesaurus/synonyms>.
MLASmart Define. "undercover thesaurus" 13 April 2015. Web. 25 September 2026. <https://smartdefine.org/undercover/thesaurus/synonyms>