Synonyms of underground

underground 1 of 3

adjective

ˈən-dər-ˌgrau̇nd 

1

as in clandestine

undertaken or done so as to escape being observed or known by others

an underground operation to smuggle ancient artifacts out of the country

Synonyms & Similar Words

• clandestine
• undercover
• covert
• sneak
• private
• sneaking
• stealth
• secret
• surreptitious
• furtive
• stealthy
• behind-the-scenes
• hole-and-corner
• sneaky
• underhanded
• undisclosed
• backstairs
• underhand
• privy
• subterranean
• hush-hush
• confidential
• hidden
• off-the-books
• closed-door
• hugger-mugger
• classified
• secreted
• restricted
• off-the-record
• top secret
• concealed
• unexposed
• back-channel
• unadvertised

Antonyms & Near Antonyms

• public
• open
• overt
• avowed
• acknowledged
• straightforward
• unrestricted
• unclassified
• obvious
• evident
• clear
• plain
• manifest
• undisguised
• unconcealed
• aboveboard
• patent

2

as in subterranean

being, situated, or operating beneath the surface of the earth

an underground shopping mall that is part of the city's subway system

Synonyms & Similar Words

• subterranean
• subsurface
• belowground

Antonyms & Near Antonyms

• surface
• aboveground

underground

2 of 3

noun

ˈən-dər-ˌgrau̇nd 

as in resistance

a secret organization in a conquered country fighting against enemy forces

joined the underground while still a teenager

Synonyms & Similar Words

• resistance
• conspiracy
• cabal

underground

3 of 3

adverb

as in undercover

Related Words

• undercover
• stealthily
• surreptitiously
• clandestinely
• secretively
• furtively
• covertly
• underhanded
• sneakily
• underhand
• underhandedly
• offstage
• collusively
• conspiratorially
• offscreen
• à deux
• inwardly
• sotto voce
• tête-à-tête
• secretly
• privately
• backstage
• intimately
• confidentially
• in camera

Dissimilar Words

• publicly
• openly

Example Sentences

Recent Examples of underground

Adjective

How to Get Started Building a Root Cellar Most root cellars are built underground or partially underground, where the surrounding earth naturally helps regulate temperature and humidity. — Helena Madden, Martha Stewart, 3 Aug. 2026

Her earliest memories are of an underground bunker, patrolled by male guards with whips, where she was imprisoned with thirty-nine older women. — Katy Waldman, New Yorker, 3 Aug. 2026

Noun

Taking the dance sensation out of New York's gay underground and on the road, the singer vogued her way around the world on her 1990 Blond Ambition Tour, which kicked off in Japan that April. — Cara Lynn Shultz, PEOPLE, 29 June 2026

When P-waves start radiating from the earthquake underground, Android phones sense the vibrations, start collecting data and send it back to Google servers for processing. — Amy Graff, New York Times, 27 June 2026

Adverb

In the monitoring room, screens blinked and maps pulsed, quietly charting what was happening underground. — Andrei Popoviciu, The Dial, 21 July 2026

The crowd is packed not only with devoted fans and freaks, but fellow musicians who also emerged from the punk rock underground decades earlier. — Steve Appleford, SPIN, 20 July 2026