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
Relevance
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
as in resistance
a secret organization in a conquered country fighting against enemy forces
joined the underground while still a teenager
Synonyms & Similar Words
as in undercover
Related Words
Dissimilar Words
Example Sentences
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Recent Examples of underground
Emma Burleigh, Fortune, 6 Nov. 2025
Guests may choose a water treatment in a pool that evokes the area’s limestone cenotes (underground wells) or try a purification by a local healer in a temazcal (a traditional heated lodge), among many other journeys for mind and body well-being.
—Robb Report Studio, Robb Report, 5 Nov. 2025
Kevin Holden Platt, Forbes.com, 9 Sep. 2025
Sibiya said the men had been killed by gas underground, their bodies carried out of the mine by colleagues and left for the police to find.
—Tommy Trenchard, NPR, 23 Aug. 2025
FOXNews.com, 29 Oct. 2025
However, the time-frame in between the pipes being built and then put underground gave Arizona skaters the perfect advantage to shred the iconic full pipes.
—Paige Moore, AZCentral.com, 28 Oct. 2025
See All Example Sentences for underground
Adjective
The tests — with buses driven in underground mines to strip away external signals — were conducted both on brand-new Yutong buses and on three-year old vehicles from Dutch bus manufacturer VDL, the company said.
—Emma Burleigh, Fortune, 6 Nov. 2025
Guests may choose a water treatment in a pool that evokes the area’s limestone cenotes (underground wells) or try a purification by a local healer in a temazcal (a traditional heated lodge), among many other journeys for mind and body well-being.
—Robb Report Studio, Robb Report, 5 Nov. 2025
Noun
But now European and American scientists are exploring whether the first human Martians could find refuge via dormant volcanos scattered across the Red Planet, inside lava tubes that criss-cross the Mars underground.
—Kevin Holden Platt, Forbes.com, 9 Sep. 2025
Sibiya said the men had been killed by gas underground, their bodies carried out of the mine by colleagues and left for the police to find.
—Tommy Trenchard, NPR, 23 Aug. 2025
Adverb
Ancient wine factory unearthed after 1,600 years underground.
—FOXNews.com, 29 Oct. 2025
However, the time-frame in between the pipes being built and then put underground gave Arizona skaters the perfect advantage to shred the iconic full pipes.
—Paige Moore, AZCentral.com, 28 Oct. 2025
See All Example Sentences for underground
Recent Examples of Synonyms for underground
Adjective
-
The 16-month plot to bribe Maduro’s chief pilot illustrates how Washington pairs clandestine operations with military power to destabilize the regime while projecting strategic pressure in the region.—
Amir Daftari,
MSNBC Newsweek,
29 Oct. 2025
-
In exchange, the agent told the pilot in a clandestine meeting, the aviator would be made a very rich man.—
Joshua Goodman,
Fortune,
28 Oct. 2025
Adjective
-
The town of about 600 sits at the northern foothills of the Smoky Mountains and offers hiking, caverns and Silver Falls, the tallest subterranean cascade in the eastern United States, according to World Atlas.—
Craig Shoup,
Nashville Tennessean,
9 Nov. 2025
-
Sweden has started construction on a similar project, and France, Canada and Switzerland are in the early stages of their subterranean disposal sites.—
Bob Woods,
CNBC,
9 Nov. 2025
Noun
-
Podrabinek captures the painful intersections between personal and political in a dissident’s life, and the solidarity that kept the resistance moving forward.—
Literary Hub,
Literary Hub,
10 Nov. 2025
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Mike seems taken aback by Nina’s stony resistance.—
Noel Murray,
Vulture,
9 Nov. 2025
Adjective
-
In the comedy's newest installment, which arrives a year after the series first premiered, Charles is assigned with helping Wheeler College president Jack Berenger (Max Greenfield) crack a case and must go undercover as a college professor, per a synopsis from Netflix.—
Brenton Blanchet,
PEOPLE,
4 Nov. 2025
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In it, viewers meet Petraitis as Andrius, who is in undercover mode; Baroti as Laima; Kasperavicius as Mykolas; and Augustaitis as Rytis.—
Georg Szalai,
HollywoodReporter,
3 Nov. 2025
Adverb
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The song – and the band – stealthily established a place in culture by assisting people through big personal moments, both in solitude and with company.—
Tom Roland,
Billboard,
16 Oct. 2025
-
Yet, the number of in-person days coming down the pipeline has been stealthily increasing.—
Nick Lichtenberg,
Fortune,
9 Oct. 2025
Adjective
-
However, his team quickly secured their covert support in the form of money and supplies.—
Literary Hub,
Literary Hub,
7 Nov. 2025
-
Trump has authorized the Central Intelligence Agency (CIA) to carry out covert operations in the country and has left the door firmly open to unspecified land operations.—
Ellie Cook,
MSNBC Newsweek,
5 Nov. 2025
Adverb
-
In a video shared Monday to the official TikTok account of Hobbiton, the charming Matamata, New Zealand, set that Wood's Frodo Baggins called home in Peter Jackson's acclaimed film trilogy, Wood surreptitiously arrives with a small armada of camera operators to document the surprise.—
Ryan Coleman,
Entertainment Weekly,
28 Oct. 2025
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The manager of Vladimir Kramnik’s opponent in that title match, Veselin Topalov, claimed the Russian was using the bathroom up to 50 times per match to surreptitiously look up chess moves on a computer — a charge that Kramnik’s manager hotly denied.—
Corky Siemaszko,
NBC news,
26 Oct. 2025
Adjective
-
Get Ready: Katy Perry Has Released a Sneak Peek of Her New Song And the internet has receipts.—
Mehera Bonner,
Marie Claire,
15 Mar. 2017
Cite this Entry
“Underground.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/underground. Accessed 11 Nov. 2025.
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