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

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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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Dissimilar Words

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
In other words, the atmosphere becomes enriched by material from underground, while also becoming depleted in some gases that astronomers would expect to see in greater abundance. — Keith Cooper, Space.com, 13 July 2026 Oncor will be upgrading critical underground electric infrastructure to improve service reliability and reduce future outage risks for customers in Dallas. — Briseida Holguin, CBS News, 13 July 2026
Noun
When oil wells are shut in, the pressure underground can become imbalanced, deforming the underlying structure. — David Goldman, CNN Money, 24 June 2026 The company now plans to demonstrate commercial-scale borehole drilling before attempting deployment of a prototype reactor underground. — Aamir Khollam, Interesting Engineering, 24 June 2026
Adverb
Three 55-gallon drums and other debris were buried underground. — Sacbee.com, 8 July 2026 Rather than choosing between unrestricted gray-market access or a blanket crackdown that simply drives use underground, the agency can chart a third way on peptides. — Jerome Adams, STAT, 6 July 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
  • Attorney Cynthia Jennings, who spoke at a press conference called several days after the police were at the treasurer’s office, had condemned social media speculation about Sierra’s action and the claims of clandestine shredding of documents.
    — Helen I. Bennett, Hartford Courant, 17 July 2026
  • That the actual, original Antifa formed in clandestine resistance to Nazi terror during the early 1930s appears lost amid the rhetorical vagaries of political propaganda.
    — Ara H. Merjian, ARTnews.com, 10 July 2026
Definition of clandestine
Adjective
  • Visitors to the park can enjoy surface and subterranean exploration, canoeing the Green River, hiking, camping, and horseback riding.
    — Josh Laskin, Travel + Leisure, 3 July 2026
  • The spa There’s a dreamy subterranean spa with all the standard treatments, but to really get into Potato Head’s groove, opt for a session at the New Age-y Sanctuary Wellness Centre instead.
    — Condé Nast, Condé Nast Traveler, 1 July 2026
Definition of subterranean
Noun
  • Shimizu voluntarily stayed in Vietnam after World War II to join the Việt Minh resistance, opposing French colonial reoccupation, the photographer explained.
    — Jacqui Palumbo, CNN Money, 14 July 2026
  • Ashley Zehnder is the CEO of Fauna Bio, a company that searches for disease resistance therapies among mammals equipped with unique adaptations.
    — Ari Daniel, NPR, 13 July 2026
Definition of resistance
Adverb
  • The noble consort takes the empress’s place, smirking, and stealthily pushes her down the stairs when no one is watching.
    — Lavender Au, The Dial, 30 June 2026
  • But did Spilotro go about life as an upstanding model citizen who rubbed elbows with the Vegas elite, while quietly and stealthily protecting the Mafia's financial interests in Vegas casinos?
    — Adam Harrington, CBS News, 23 June 2026
Definition of stealthily
Adjective
  • The complaint was the result of a months-long investigation in which undercover operators posed as prospective tenants and recorded phone calls with Greystar employees to test their compliance with the law.
    — Jack Flemming, Los Angeles Times, 15 July 2026
  • The Chicago Police Department also carries out undercover stings at small massage parlors after the city receives complaints of vice activity.
    — Sam Charles, Chicago Tribune, 13 July 2026
Definition of undercover
Adverb
  • Instead, the technology is surreptitiously marketing authoritarian political narratives to policy makers, scholars, and readers around the world.
    — Michael Schuman, The Atlantic, 7 July 2026
  • As a group of dancers surrounded her on the B-stage, she was surreptitiously harnessed into a rig that carried her aloft, limp yet belting, into the heavens, or at least into what looked like a UFO hovering over the arena.
    — Chris Willman, Variety, 7 June 2026
Definition of surreptitiously
Adjective
  • These functions can be critical in various applications and scenarios, such as inspections, covert surveillance, search-and-rescue operations, disaster monitoring, and agricultural pest tracking.
    — New Atlas, New Atlas, 18 July 2026
  • Although, with words like emergency and bunker—the skeptics have made routine election work seem like a covert-ops thriller.
    — Hanna Rosin, The Atlantic, 16 July 2026
Definition of covert
Adverb
  • Soon afterward, social media commenters were speculating about whether Sierra broke into the office or was caught clandestinely shredding documents.
    — Don Stacom, Hartford Courant, 10 July 2026
  • This great disparity between reality and story, truth and history, takes on new dimensions when Robin clandestinely takes refuge at an island priory where Sister Brigid (Jodie Comer) tends to his wounds.
    — ABC News, ABC News, 17 June 2026
Definition of clandestinely

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undergraduates
underground
undergrounds
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Cite this Entry

“Underground.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/underground. Accessed 18 Jul. 2026.

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More from Merriam-Webster on underground

Nglish: Translation of underground for Spanish Speakers

Britannica.com: Encyclopedia article about underground

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