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
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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
Synonyms & Similar Words
Antonyms & Near Antonyms
Example Sentences
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Recent Examples of underground
Andrew McKean, Outdoor Life, 22 May 2025
In recent years, instead of going for experimental looks, reminiscent of underground London, she’s opted for the classics like French bobs and natural beats.
—India Espy-Jones, Essence, 22 May 2025
Benjamin Weinthal, FOXNews.com, 19 Apr. 2025
Long-Term Burial: Calcium carbonate mineral precursors, such as calcite, undergo transformation into dolomite after being buried, facilitated by slowly rising temperatures (ranging between 60 to 100 degrees Celsius) underground.
—David Bressan, Forbes.com, 8 Apr. 2025
Antonio Maria Delgado, Miami Herald, 19 May 2025
On top of that, potato plants do most of their growing underground and may compete with watermelons for soil space.
—Lauren Landers, Better Homes & Gardens, 17 May 2025
See All Example Sentences for underground
Adjective
The company plans to develop an underground copper, nickel, cobalt, and platinum metals mine about nine miles southeast of Ely, the gateway community to the Boundary Waters.
—Andrew McKean, Outdoor Life, 22 May 2025
In recent years, instead of going for experimental looks, reminiscent of underground London, she’s opted for the classics like French bobs and natural beats.
—India Espy-Jones, Essence, 22 May 2025
Noun
Hannah said Iran’s secretive underground Fordow nuclear fuel enrichment plant and Natanz nuclear site were where Iran was caught digging tunnels in the mountains.
—Benjamin Weinthal, FOXNews.com, 19 Apr. 2025
Long-Term Burial: Calcium carbonate mineral precursors, such as calcite, undergo transformation into dolomite after being buried, facilitated by slowly rising temperatures (ranging between 60 to 100 degrees Celsius) underground.
—David Bressan, Forbes.com, 8 Apr. 2025
Adverb
According to Morán, nearly all top members of the main opposition party, Vente Venezuela, have either been arrested or forced underground.
—Antonio Maria Delgado, Miami Herald, 19 May 2025
On top of that, potato plants do most of their growing underground and may compete with watermelons for soil space.
—Lauren Landers, Better Homes & Gardens, 17 May 2025
See All Example Sentences for underground
Recent Examples of Synonyms for underground
Adjective
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Tired of using bulky night vision goggles for your clandestine nocturnal activities?—
Jennifer Ouellette,
ArsTechnica,
22 May 2025
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The fiery combination of Mars trine Venus sparks things up in your clandestine 12th house of secrets and eighth house of intimate affairs.—
Valerie Mesa,
People.com,
22 May 2025
Adjective
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Naked mole rats – a social, subterranean cold-blooded mammal that looks like a hot dog with teeth – generate fevers in response to infection, despite their unusual physiology.—
Harry Bernheim,
The Conversation,
23 May 2025
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Rounding it all out: a lengthy double-gated driveway that passes between a pair of matching 2,000-square-foot carriage houses and over a bridge before emptying out at a circular motor court, along with an eight-car garage complemented by a subterranean six-car garage for all your toys.—
Wendy Bowman,
Robb Report,
23 May 2025
Noun
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Some adaptations to infectious pathogens came at a cost, however: strengthening resistance to ancient diseases might have elevated the likelihood of immune overreaction.—
Kermit Pattison,
Scientific American,
20 May 2025
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But the package faces mounting resistance from both ends of the Republican Party.—
Nik Popli,
Time,
20 May 2025
Adjective
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Over the course of the investigation, Salinas Valencia sold the undercover officer several firearms, including two machineguns, as well as fentanyl pills and cocaine.—
Brian Bell,
The Orlando Sentinel,
22 May 2025
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Officer 18 was a standout among undercover officers, doubling his or her regular pay all three years.—
Ariane Lange,
Sacbee.com,
20 May 2025
Adjective
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Striking Iran’s nuclear program would likely set off a much larger conflict in which Israel and the United States hunt for covert Iranian nuclear sites and Tehran retaliates in the Middle East and beyond.—
Richard Nephew,
Foreign Affairs,
26 May 2025
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Mon Mothma's speech Mon Mothma's covert support of the Rebels becomes public following the devastating events of the Ghorman Massacre.—
Nick Romano,
EW.com,
25 May 2025
Adjective
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The museums are typically built in the presidents’ home states with private donations and endowments.—
Swapna Venugopal Ramaswamy,
USA Today,
26 May 2025
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The center, which does not receive government funding, relies solely on private donations to keep their programs and facility up and running.—
Toria Sheffield,
People.com,
26 May 2025
Cite this Entry
“Underground.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/underground. Accessed 3 Jun. 2025.
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