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
Mirna Alsharif, NBC news, 7 Mar. 2026
The reserve, which can reach as many as 714 million barrels, is stored in large, high-security underground salt caverns along the gulf coastlines of Louisiana and Texas.
—Max Zahn, ABC News, 6 Mar. 2026
Donnelle Eller, Des Moines Register, 13 Feb. 2026
Reasons for living underground The first rule of both shows?
—Richard Edwards, Space.com, 7 Feb. 2026
Ken Toltz, Denver Post, 5 Mar. 2026
One of the eight wonders of Kansas lies 650 feet underground in Hutchinson, the only salt mine in the United States that operates an underground museum open to tourists.
—Lisa Gutierrez, Kansas City Star, 4 Mar. 2026
See All Example Sentences for underground
Adjective
The Israeli military has released footage of a strike on an underground bunker that was built for Ayatollah Ali Khamenei.
—Mirna Alsharif, NBC news, 7 Mar. 2026
The reserve, which can reach as many as 714 million barrels, is stored in large, high-security underground salt caverns along the gulf coastlines of Louisiana and Texas.
—Max Zahn, ABC News, 6 Mar. 2026
Noun
But only a small portion of CO2 can be reused, and Broin said the industry still needs access to a pipeline in states like Iowa that lack the geological capability to sequester carbon dioxide underground.
—Donnelle Eller, Des Moines Register, 13 Feb. 2026
Reasons for living underground The first rule of both shows?
—Richard Edwards, Space.com, 7 Feb. 2026
Adverb
Since Saturday morning, much of our community life has shifted underground.
—Ken Toltz, Denver Post, 5 Mar. 2026
One of the eight wonders of Kansas lies 650 feet underground in Hutchinson, the only salt mine in the United States that operates an underground museum open to tourists.
—Lisa Gutierrez, Kansas City Star, 4 Mar. 2026
See All Example Sentences for underground
Recent Examples of Synonyms for underground
Adjective
-
The documentary is built around the investigative work of journalists Katya Hakim and Denis Korotkov who picked up the mantle from three colleagues who were brutally slain while looking into Wagner’s clandestine activities in Africa.—
Matthew Carey,
Deadline,
10 Mar. 2026
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On this occasion in 2018, Rodriguez and others in the group had received an anonymous tip of a possible clandestine cemetery on the outskirts of Cordoba.—
Kamala Thiagarajan,
NPR,
8 Mar. 2026
Adjective
-
The spa In the subterranean 6,800 square-foot space, therapists give deep-scrub facials in black Italian-marble treatment rooms.—
Condé Nast,
Condé Nast Traveler,
7 Mar. 2026
-
The professional-use treatments are effective against Formosan termites at the same concentration levels used for native subterranean termites.—
Arricca Elin SanSone,
Southern Living,
6 Mar. 2026
Noun
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As political attacks on trans rights intensify, Calamia’s visibility as both athlete and activist represents an act of resistance and hope.—
Deborah Vankin,
Los Angeles Times,
6 Mar. 2026
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Panahi’s main talking point for the rest of the interview was that everyday resistance is no big whoop.—
Bethy Squires,
Vulture,
6 Mar. 2026
Adjective
-
Herlihy goes undercover as Jost, even appearing on the Late Night with Seth Meyers show.—
Andy Hoglund,
Entertainment Weekly,
8 Mar. 2026
-
Nick warned Mindi that an undercover team disguised as tree surgeons were planting surveillance cameras around their house.—
Erin Moriarty,
CBS News,
8 Mar. 2026
Adverb
-
Faced with rising electricity prices, Americans are stealthily adding DIY solar systems.—
Alexandra Banner,
CNN Money,
5 Mar. 2026
-
Why did the actor and Oscar-winning filmmaker stealthily start exploring the technology that is giving Hollywood such existential angst?—
Dade Hayes,
Deadline,
5 Mar. 2026
Adjective
-
None could tame its political furies; its covert operations, which killed more than a thousand Americans in Lebanon, Iraq, and Afghanistan; or its expansion, through the creation of like-minded extremist movements, across the Middle East.—
Robin Wright,
New Yorker,
8 Mar. 2026
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Minneapolis psychologist Lucy Olson helped organize a covert grassroots network that swelled to 2,000 volunteers assisting around 500 immigrant families with legal matters, shelter, food and rent assistance.—
Steve Karnowski,
Chicago Tribune,
7 Mar. 2026
Adverb
-
But tech companies will have to prove that new devices can do things better or differently than smartphones and alleviate privacy concerns around devices can surreptitiously record their surroundings.—
Lisa Eadicicco,
CNN Money,
2 Mar. 2026
-
Also, strong steps against the Russian shadow fleet that surreptitiously transports energy products, designation of Russia as a State Sponsor of Terrorism, and other economic measures strongly penalizing Russia and aiding Ukraine.—
U.S. Sen. Richard Blumenthal,
Hartford Courant,
28 Feb. 2026
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 12 Mar. 2026.
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