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

The result was the equivalent of an X-ray of the subsurface extending roughly 300 feet underground, without drilling a single hole. — Nolan Roth, Scientific American, 23 Aug. 2026

Once an extensive underground network of rhizomes develops, Messinger explains that complete removal becomes considerably more difficult. — Sj McShane, Martha Stewart, 23 Aug. 2026

Noun

Her work has included uncovering human trafficking networks, revealing an ISIS underground torture prison in Syria, documenting the war in Ukraine and interviewing senior political figures and world leaders. — Efrat Lachter, FOXNews.com, 30 July 2026

For the past half-decade, evilgiane and his Surf Gang collective have had their hands all over the quirkiest and most effervescent sounds of rap’s underground and mainstream. — Oba Awolowo, Pitchfork, 3 July 2026

Adverb

For decades, energy geologists thought hydrogen molecules were too small and light to stay trapped underground without leaking away. — Aman Tripathi, Interesting Engineering, 20 Aug. 2026

And in their relationship with fungi there is more still, underground. — Literary Hub, 20 Aug. 2026