2
unfathomable
2
unintelligible(clandestine, underground, undisclosed, concealment)
2
unpublished(adjective, clandestine, underground, undisclosed)
2
unseen(adjective, secret, unknown, hidden, imperceptible)
1
cloak
1
abandoned(close, quiet, private, isolated, secluded)
1
abri
1
aerie
1
air-raid shelter
1
alchemistic(strange, unknown, curious, concealed, inexplicable)
1
aloof(close, quiet, private, isolated, secluded)
1
anonymously
1
arbor
1
armored
1
artful(mean, smooth, cunning, knowing, sly)
1
astrological(strange, unknown, curious, concealed, inexplicable)
1
back door
1
backdoor(clandestine, underground, undisclosed)
1
backstair
1
baldachin
11 years ago|17k views|share |citing 
APASmart Define. (2015). covert thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/covert/thesaurus/synonyms
ChicagoSmart Define. 2015. "covert thesaurus" https://smartdefine.org/covert/thesaurus/synonyms (accessed September 21, 2026).
HarvardSmart Define 2015, covert thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/covert/thesaurus/synonyms>.
MLASmart Define. "covert thesaurus" 10 April 2015. Web. 21 September 2026. <https://smartdefine.org/covert/thesaurus/synonyms>