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
Ashley Miznazi, Miami Herald, 9 Apr. 2026
There is currently no permanent underground disposal facility for commercial nuclear waste operational anywhere in the world.
—James Brooks, Los Angeles Times, 9 Apr. 2026
Virginia Chamlee, PEOPLE, 18 Apr. 2026
The same goes for the Pixies, one of the most influential bands ever from the American underground, inspiring Nirvana and all that followed — yet never nominated.
—Rob Sheffield, Rolling Stone, 15 Apr. 2026
Lauren Landers, Better Homes & Gardens, 17 Apr. 2026
Less than half a mile from Egger’s home, the smell is overwhelming where the river shoots out of pipes after being forced briefly underground near Saturn Boulevard.
—ABC News, 16 Apr. 2026
See All Example Sentences for underground
Adjective
The problem was widespread throughout the county as gas stations used steel underground storage containers that were highly corrosive, especially in coastal communities.
—Ashley Miznazi, Miami Herald, 9 Apr. 2026
There is currently no permanent underground disposal facility for commercial nuclear waste operational anywhere in the world.
—James Brooks, Los Angeles Times, 9 Apr. 2026
Noun
More than 60 radio stations from Boston to Tulsa have banned the song, but through word of mouth and the FM underground, 'The Pill' is selling 15,000 copies a week.
—Virginia Chamlee, PEOPLE, 18 Apr. 2026
The same goes for the Pixies, one of the most influential bands ever from the American underground, inspiring Nirvana and all that followed — yet never nominated.
—Rob Sheffield, Rolling Stone, 15 Apr. 2026
Adverb
Groundhogs are most active in spring and summer but spend their winters underground hibernating.
—Lauren Landers, Better Homes & Gardens, 17 Apr. 2026
Less than half a mile from Egger’s home, the smell is overwhelming where the river shoots out of pipes after being forced briefly underground near Saturn Boulevard.
—ABC News, 16 Apr. 2026
See All Example Sentences for underground
Recent Examples of Synonyms for underground
Adjective
-
Darrell Lee Vannostran, 40, was booked after he was arrested for the use of photo or video equipment in a clandestine manner in a private place.—
Sarah Rumpf-Whitten,
FOXNews.com,
22 Apr. 2026
-
In January, authorities announced more than 1,500 pounds of meth were seized from clandestine laboratories in the states of Durango, Sinaloa and Michoacán.—
CBS News,
CBS News,
21 Apr. 2026
Adjective
-
Endangered amphibians in California include the desert slender salamander, a subterranean amphibian found in just two spots in Riverside County.—
Sarah Linn,
Sacbee.com,
22 Apr. 2026
-
Take 25 Hours, in Long Island City, for example, which is freighted with a depressing ambience that is equal parts chemistry lab and subterranean grotto.—
Vince Aletti,
New Yorker,
17 Apr. 2026
Noun
-
The stable Taurus Sun meets resistance from intense Pluto in Aquarius, pushing tension between daily responsibilities and bigger career demands.—
Tarot.com,
New York Daily News,
25 Apr. 2026
-
The potential schedule change could further complicate a public-private project that has encountered steady resistance since it was announced two years ago.—
Gayla Cawley,
Boston Herald,
24 Apr. 2026
Adjective
-
However, the user was, in fact, an undercover detective with the HCSO, documents said.—
Bonny Chu,
FOXNews.com,
20 Apr. 2026
-
But the charges were quickly dropped by the Brooklyn District Attorney’s Office — and police admitted Brown turned out not to be the man cops were seeking for taking money from a drug dealer after the dealer sold crack to an undercover cop near the store.—
Rocco Parascandola,
New York Daily News,
20 Apr. 2026
Adverb
-
Her foundation, Yield Giving, has been stealthily donating billions since 2020 with no strings attached.—
Emma Burleigh,
Fortune,
13 Apr. 2026
-
As part of the Virginia-class fleet, USS New Jersey forms a central element of the US attack-submarine force, designed to operate stealthily in both littoral zones and open-ocean environments, providing the Navy with a versatile and survivable platform for modern undersea warfare.—
Bojan Stojkovski,
Interesting Engineering,
4 Apr. 2026
Adjective
-
Other such discrimination is more covert.—
Alison Somin,
Oc Register,
10 Apr. 2026
-
The hypoallergenic, 100-percent cotton fabric provides a breathable option for covert breastfeeding.—
Pamela Brill,
Parents,
7 Apr. 2026
Adverb
-
Katas wan't recording in the front seat, so Christine, seated beside the wives in the back, surreptitiously pulled out her phone to record Bateman.—
Ryan Coleman,
Entertainment Weekly,
8 Apr. 2026
-
Trump may have also relieved pressure on Democrats to surreptitiously help one of the Republicans to leap ahead, so as to avoid a 1-2 GOP outcome.—
Dan Walters,
Oc Register,
6 Apr. 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 26 Apr. 2026.
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