underground 1 of 3

adjective

ˈən-dər-ˌgrau̇nd How to pronounce underground (audio)
Definition of undergroundnext
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

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Antonyms & Near Antonyms
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

Antonyms & Near Antonyms

underground

2 of 3

noun

ˈən-dər-ˌgrau̇nd How to pronounce underground (audio)
as in resistance
a secret organization in a conquered country fighting against enemy forces joined the underground while still a teenager

Synonyms & Similar Words

underground

3 of 3

adverb

as in undercover

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Example Sentences

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Recent Examples of underground
Adjective
The demand has grown so high that an underground gray market has flourished in delivering those cult-classic burgers to hungry customers. — Tatiana Sataua, Fortune, 21 Oct. 2026 However, the macro networks our industry has engineered outdoors were never designed to penetrate deep underground or dense interiors. — Stephen Farrugia, Forbes.com, 20 Oct. 2026
Noun
The satellites chase each other in orbit to measure gravitational shifts in water mass, both on land and underground. — Ian James, Los Angeles Times, 24 Sep. 2026 Since the late 1990s, taxpayers have been funding a program to stash extra Colorado River water underground, with the idea that it could be used as a backup in times of shortage. — Alex Hager, NPR, 31 Aug. 2026
Adverb
Slickwater uses a mix of water, sand, and thin, friction-reducing chemicals rather than thicker gels to shatter dense shale rock deep underground and free the gas. — Jordan Blum, Fortune, 10 Oct. 2026 Think about how trees communicate with each other through their network of roots underground. — Clare Marie Schneider, NPR, 10 Oct. 2026 See All Example Sentences for underground
Recent Examples of Synonyms for underground
  1. clandestine
  2. subterranean
  3. resistance
  4. stealthily
  5. undercover
  6. surreptitiously
  7. covert
  8. clandestinely
Adjective
  • There was something sad in our meetups always having to be clandestine.
    — Erica Garza, Los Angeles Times, 30 Oct. 2026
  • The arrest, the official explained, came after the Attorney General’s Office concluded that there had been misconduct in an April operation in which state officials dismantled a clandestine drug-manufacturing laboratory.
    — Mauricio Torres, CNN Money, 18 Oct. 2026
Definition of clandestine
Adjective
  • The first subterranean fish known to live in the Ganges basin was discovered after zoologists spotted it on TikTok and pumped it out of a borehole.
    — J. B. MacKinnon, Harpers Magazine, 27 Oct. 2026
  • Israel launched a ground invasion following an extensive aerial bombardment of Hamas’s military infrastructure, including its vast network of subterranean tunnels.
    — Eric Cortellessa, Time, 25 Oct. 2026
Definition of subterranean
Noun
  • By understanding how these products evolve and diversify in bacteria, scientists might be able to tackle current resistance that humans have developed to some of the antibiotics that exist.
    — Maria Mocerino, Interesting Engineering, 24 Oct. 2026
  • In the hills surrounding Taiz, the government forces are trying to repel the Houthis but face stiff resistance, especially east of the city.
    — ABC News, ABC News, 24 Oct. 2026
Definition of resistance
Adverb
  • These two are almost too good at stealthily murdering soldiers in the dead of night.
    — Maggie Fremont, Vulture, 23 Oct. 2026
  • Ever since Air France rolled out its new La Première service in 2025, the French flag carrier has stealthily risen to the top of the First Class food chain.
    — Laura Dannen Redman, Robb Report, 22 Oct. 2026
Definition of stealthily
Adjective
  • An unverified Snapchat message, which students in France claim was written by an undercover police officer, has become the slogan of student protests.
    — Joseph Ataman, CNN Money, 24 Oct. 2026
  • From that moment on, Liang went all-in on becoming the beloved fighter, putting herself through an intense physical transformation to embody the undercover Interpol agent.
    — Brian Davids, HollywoodReporter, 23 Oct. 2026
Definition of undercover
Adverb
  • The centerpiece of the government’s case is that the defendants surreptitiously drugged women.
    — Kara Scannell, CNN Money, 25 Oct. 2026
  • For years, scammers would surreptitiously install skimming devices on card readers at ATMs, gas pumps and corner stores.
    — Eli Hager, ProPublica, 13 Oct. 2026
Definition of surreptitiously
Adjective
  • Anthropic also wants to investigate covert misalignment, where models conceal their intentions instead of openly displaying concerning behavior.
    — Aamir Khollam, Interesting Engineering, 31 Oct. 2026
  • Tehran denies involvement, but the incident raises the prospect of covert operations against American military assets beyond the Middle East.
    — Hamidreza Azizi, Time, 27 Oct. 2026
Definition of covert
Adverb
  • In 1983, Baker and Casey became embroiled in a public dispute over who had clandestinely obtained Jimmy Carter’s briefing book for the 1980 Presidential debate.
    — Bob Woodward, New Yorker, 19 Oct. 2026
  • Because Iran is a theocratic dictatorship that routinely arrests and in some cases executes journalists, Western reporters hoping to cover the country must either work clandestinely or submit to government supervision.
    — James Kirchick, The Atlantic, 29 July 2026
Definition of clandestinely

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Cite this Entry

“Underground.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/underground. Accessed 2 Nov. 2026.

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Britannica.com: Encyclopedia article about underground

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