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
Tom Tapp, Deadline, 15 Oct. 2025
Many parallels exist between being high above the Earth and deep underground.
—Kenna Hughes-Castleberry, Space.com, 14 Oct. 2025
Joshua Siskin, Oc Register, 25 Oct. 2025
In 1944, Republicans called the construction of an underground bunker and offices within the East Wing wasteful and accused FDR of using the White House makeover to improve his image, the WHHA said on its website.
—Ryan Mancini, The Hill, 24 Oct. 2025
Tommy Trenchard, NPR, 23 Aug. 2025
Millions of Americans own the rights to oil and gas underground.
—Jacob Orledge, ProPublica, 15 Aug. 2025
See All Example Sentences for underground
Adjective
A week later the same fire, which had likely smoldered underground, reemerged and became known as the Palisades Fire.
—Tom Tapp, Deadline, 15 Oct. 2025
Many parallels exist between being high above the Earth and deep underground.
—Kenna Hughes-Castleberry, Space.com, 14 Oct. 2025
Noun
Along with bulbs, tubers, and rhizomes, corms constitute the quartet of underground storage structures that send up their silky blooms once a year — or more, in the case of remontant (repeat-blooming) irises and daylilies.
—Joshua Siskin, Oc Register, 25 Oct. 2025
In 1944, Republicans called the construction of an underground bunker and offices within the East Wing wasteful and accused FDR of using the White House makeover to improve his image, the WHHA said on its website.
—Ryan Mancini, The Hill, 24 Oct. 2025
Adverb
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
Millions of Americans own the rights to oil and gas underground.
—Jacob Orledge, ProPublica, 15 Aug. 2025
See All Example Sentences for underground
Recent Examples of Synonyms for underground
Adjective
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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
-
If substantiated, Russia's use of a maritime disaster site for clandestine military purposes represents both a security threat and a sensitive violation of an international agreement aimed at honoring the victims.—
Jordan King,
MSNBC Newsweek,
24 Oct. 2025
Adjective
-
The subterranean passageway shown to her by a residence staffer provided some relief.—
Darlene Superville,
Denver Post,
26 Oct. 2025
-
The hotel's new subterranean spa will debut in spring 2026 with a full slate of wellness offerings.—
Sarah Bruning,
Travel + Leisure,
24 Oct. 2025
Noun
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Reagan empowered Afghanistan’s resistance to the Soviet invasion – escalating Soviet losses and fueling discontent.—
Kathleen Collins,
Twin Cities,
26 Oct. 2025
-
The shelter had initially been targeted for a July 2025 opening, and has encountered fierce resistance from parts of the West Roxbury community since the state first began sharing its intention to house homeless families there last spring.—
Gayla Cawley,
Boston Herald,
26 Oct. 2025
Adjective
-
Billitier did have a hell of a story to tell about his decades of undercover work for the FBI, including several years infiltrating a Colombian drug ring in Texas.—
Steve Belanger,
HollywoodReporter,
23 Oct. 2025
-
The movie is based on the 1980s TV series, starring Don Johnson and Philip Michael Thomas, as undercover detectives in South Florida.—
Angelique Jackson,
Variety,
23 Oct. 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
-
The Institute for the Study of War (ISW) said on Friday the incident and the recent air incursion linked to Moscow show Kremlin plans for covert and overt attacks against Europe to prepare for a possible NATO-Russia war.—
Brendan Cole,
MSNBC Newsweek,
25 Oct. 2025
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The device is intended for intelligent underwater detection, real-time environmental monitoring, and potentially covert reconnaissance missions worldwide.—
Bojan Stojkovski,
Interesting Engineering,
25 Oct. 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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Pavlick allegedly placed the camera under the toilet seat and surreptitiously videotaped dozens of adults and children, police said, KCRG reports.—
KC Baker,
PEOPLE,
21 Oct. 2025
Adjective
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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 29 Oct. 2025.
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