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
Luisa Zargani, Footwear News, 19 June 2026
Install underground fencing and remove food sources to keep pests out.
—Abby Monteil, The Spruce, 19 June 2026
Joe Yogerst, Forbes.com, 28 May 2026
When oil wells are shut in, the pressure underground can become imbalanced, deforming the underlying structure.
—David Goldman, CNN Money, 27 May 2026
Mrigakshi Dixit, Interesting Engineering, 17 June 2026
With reddish-brown bodies, fire ants travel in swarms and build large colonies deep underground.
—Olivia McIntosh, Martha Stewart, 17 June 2026
See All Example Sentences for underground
Adjective
The women’s store will be expanded, and the two units will be linked by a new underground passage.
—Luisa Zargani, Footwear News, 19 June 2026
Install underground fencing and remove food sources to keep pests out.
—Abby Monteil, The Spruce, 19 June 2026
Noun
Visitors help the staff dig and build a traditional imu underground with volcanic rocks, banana stumps, ti leaves and burlap sacks, and then fill the pit with mea ʻai staples like kālua pork, chicken, taro, yams and breadfruit.
—Joe Yogerst, Forbes.com, 28 May 2026
When oil wells are shut in, the pressure underground can become imbalanced, deforming the underlying structure.
—David Goldman, CNN Money, 27 May 2026
Adverb
The plan is to compress the green hydrogen gas and pump it deep underground for storage within custom-engineered, lined rock caverns.
—Mrigakshi Dixit, Interesting Engineering, 17 June 2026
With reddish-brown bodies, fire ants travel in swarms and build large colonies deep underground.
—Olivia McIntosh, Martha Stewart, 17 June 2026
See All Example Sentences for underground
Recent Examples of Synonyms for underground
Adjective
-
Some may be announced publicly; others may happen in more clandestine ways.—
Eben Novy-Williams,
Sportico.com,
10 June 2026
-
But clandestine flows aren’t the biggest factor behind the market calm.—
Matt Egan,
CNN Money,
9 June 2026
Adjective
-
Then comes the subterranean twist.—
Mrigakshi Dixit,
Interesting Engineering,
17 June 2026
-
Be sure to hit the subterranean SoWa Vintage Market for thrifting finds, and on weekends from spring through fall the outdoor SoWa Open Market sets up shop with local vendors, artisans, food purveyors, farmers, and food and drink trucks selling their wares in a fun, alfresco setting.—
Shannon McMahon,
Condé Nast Traveler,
17 June 2026
Noun
-
There’s a dry, droll seam of generation-gap humor in George’s continued, failed attempts to insert himself as a father figure into the life of someone who never asked for one, and Zeke’s blankly bemused resistance to his efforts.—
Guy Lodge,
Variety,
19 June 2026
-
The plan to buy large warehouses unfit for human habitation and spend millions more to convert them to prisons sparked nationwide backlash and pointed resistance in Social Circle and Oakwood.—
AJ Willingham,
AJC.com,
19 June 2026
Adverb
-
The six-suite Baines’ Lodge, though, has stealthily sneaked past them all as an existing camp that has received a thoughtful, artful makeover from operator Abercrombie & Kent.—
Todd Plummer,
Robb Report,
19 June 2026
-
Ernest has been stealthily making deals, investing nearly $500 million into some of the world’s hottest technology companies, including SpaceX, Anthropic and Jeff Bezos’ new artificial intelligence startup, Prometheus, which is the firm’s largest investment to date.—
Mirtha Donastorg,
AJC.com,
17 June 2026
Adjective
-
According to his plea agreement with prosecutors, Doyle sold a Glock pistol to an undercover informant on May 20, 2025 — part of a series of transactions on Chicago’s South Side that led to his arrest on July 7, 2025, a few days after the shooting at his daughter’s party.—
Sam Charles,
Chicago Tribune,
22 June 2026
-
Whether openly or undercover, MSV doesn’t just fail shareholders.—
Steve Denning,
Forbes.com,
21 June 2026
Adverb
-
As a group of dancers surrounded her on the B-stage, she was surreptitiously harnessed into a rig that carried her aloft, limp yet belting, into the heavens, or at least into what looked like a UFO hovering over the arena.—
Chris Willman,
Variety,
7 June 2026
-
Gray-hat hackers, unlike white-hats, surreptitiously sneak into corporate systems to find security vulnerabilities.—
Winston Cho,
HollywoodReporter,
4 June 2026
Adjective
-
The film follows cybersecurity expert Daniel Kellner (Josh O’Connor), who lifts secret files about the existence of aliens from Wardex, a covert non-government organization that used to employ him.—
Tim Lammers,
Forbes.com,
13 June 2026
-
The investigation also linked the activity to China based on IP addresses associated with a LinkedIn account and a Gmail account tied to the covert recruitment scheme.—
Michael Kan,
PC Magazine,
10 June 2026
Adverb
-
This great disparity between reality and story, truth and history, takes on new dimensions when Robin clandestinely takes refuge at an island priory where Sister Brigid (Jodie Comer) tends to his wounds.—
ABC News,
ABC News,
17 June 2026
-
Other examples of politically motivated pirate radio can be found around the world, some of them clandestinely backed by governmental intelligence agencies, but many of them existing as truly grassroots endeavors.—
Encyclopedia Britannica,
Encyclopedia Britannica,
23 Apr. 2026
Cite this Entry
“Underground.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/underground. Accessed 24 Jun. 2026.
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