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
Kaif Shaikh, Interesting Engineering, 27 Mar. 2026
Separate natural gas explosions in January 2024 that destroyed two homes in Jackson, Mississippi resulted from underground pipes pulling loose from their fittings as spongy clay soil expanded and contracted with rainfall, according to a federal report released Thursday.
—ABC News, 26 Mar. 2026
Cami Koons, Iowa Capital Dispatch, 17 Feb. 2026
Montreal’s underground is the RÉSO.
—Vivian Song, CNN Money, 17 Feb. 2026
Christopher Bonanos, Curbed, 25 Mar. 2026
Natural gas is a fossil-fuel energy source extracted from deep underground where organic matter, under immense pressure and heat, turns into methane and other gases over millions of years.
—Stephanie Pappas, Scientific American, 23 Mar. 2026
See All Example Sentences for underground
Adjective
These are underground complexes used to store and launch ballistic missiles.
—Kaif Shaikh, Interesting Engineering, 27 Mar. 2026
Separate natural gas explosions in January 2024 that destroyed two homes in Jackson, Mississippi resulted from underground pipes pulling loose from their fittings as spongy clay soil expanded and contracted with rainfall, according to a federal report released Thursday.
—ABC News, 26 Mar. 2026
Noun
While the concept of finding naturally occurring stores of hydrogen underground is relatively new, Johnson said the process of drilling and producing hydrogen wells is well established science and uses the same rigs used to drill for natural gas.
—Cami Koons, Iowa Capital Dispatch, 17 Feb. 2026
Montreal’s underground is the RÉSO.
—Vivian Song, CNN Money, 17 Feb. 2026
Adverb
Although most stations are now wired so mobile phones can be used underground, the signal is often much weaker and the data throughput slower than above.
—Christopher Bonanos, Curbed, 25 Mar. 2026
Natural gas is a fossil-fuel energy source extracted from deep underground where organic matter, under immense pressure and heat, turns into methane and other gases over millions of years.
—Stephanie Pappas, Scientific American, 23 Mar. 2026
See All Example Sentences for underground
Recent Examples of Synonyms for underground
Adjective
-
The Pozo de Vargas is considered the largest clandestine mass grave of Argentina’s last dictatorship with the remains of 149 people recovered from the site.—
Débora Rey,
Los Angeles Times,
24 Mar. 2026
-
The Pozo de Vargas is considered the largest clandestine mass grave of Argentina’s last dictatorship with the remains of 149 people recovered from the site.—
ABC News,
ABC News,
22 Mar. 2026
Adjective
-
The spa The serene, partially subterranean spa has seven treatment rooms, hammams, saunas, and a spacious relaxation area.—
Condé Nast,
Condé Nast Traveler,
28 Mar. 2026
-
The groundwater flowing through the subterranean cave systems of central Texas are vital for both farming and daily life.—
Andrew Paul,
Popular Science,
26 Mar. 2026
Noun
-
Nooshin Meshkaty, an Iranian American businessperson, said even though the government has tried to limit people for 47 years, it has always been met with resistance.—
Laurie Perez,
CBS News,
28 Mar. 2026
-
As playful as the movie is, its central tale of persecution and resistance plays not like an allegory but like a communion, a linking of the times—the inspiration of conscience by the revelation of past heroism, political and artistic.—
Richard Brody,
New Yorker,
27 Mar. 2026
Adjective
-
Some of the ammunition was purchased from co-conspirators by undercover officers, prosecutors said.—
Sierra van der Brug,
Oc Register,
31 Mar. 2026
-
Working with a different undercover officer, this time in a European city, Chalker successfully extracted Bernadine to America.—
David D. Kirkpatrick,
New Yorker,
30 Mar. 2026
Adverb
-
Such cerebral, stealthily political dramas have made Petzold an auteur’s auteur, beloved by the likes of Claire Denis and Brady Corbet.—
Holden Seidlitz,
New Yorker,
20 Mar. 2026
-
But the major platform of the Oscars also brings another level of exposition, which is not always beneficial for a documentary director trying to move stealthily and precisely.—
Rafa Sales Ross,
Variety,
20 Mar. 2026
Adjective
-
Her covert affair with Davis became big news when a Chicago gossip columnist wrote a detailed account of their relationship in early 1958, including their plans to wed, despite their denials.—
Glenn Garner,
Deadline,
28 Mar. 2026
-
While Iran is not known to have any interests in Uganda, it has been accused of covert operations in neighboring Kenya and Tanzania, including the running of smuggling networks and making controversial diplomatic and economic outreach with questionable motives throughout the region.—
Paul Tilsley,
FOXNews.com,
28 Mar. 2026
Adverb
-
Maritime tracking firm Winward suggested the ship may have spoofed its location and surreptitiously delivered the fuel to Cuba already.—
Nora Gámez Torres,
Miami Herald,
20 Mar. 2026
-
Slipping surreptitiously from documentary to drama, the story of Junyi, a Catalan of Chinese decent, and his embrace of his roots, moved by the singular draw of family history, and with that a multi-cultural identity.—
Ed Meza,
Variety,
10 Mar. 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 2 Apr. 2026.
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