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
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Recent Examples of underground
Condé Nast, Condé Nast Traveler, 3 Apr. 2026
Exhibitors include Nicola Bulgari, who keeps part of his vast car collection in an underground garage in central Rome, and sponsors include Swiss bank UBS, Gulfstream, Richard Mille, and RM Sotheby’s.
—Ben Oliver, Robb Report, 3 Apr. 2026
Rupendra Brahambhatt, Interesting Engineering, 22 Feb. 2026
Decades after that, when hoists fell silent in 1975, Bisbee’s underground ran for more than 2,000 miles on roughly 43 levels—a city folded beneath a town of just five square miles.
—Masha Hamilton, Longreads, 19 Feb. 2026
Nancy A. Youssef, The Atlantic, 31 Mar. 2026
More broadly, the discovery highlights hidden biodiversity in groundwater systems and suggests older evolutionary lineages preserved underground.
—Hanna Wickes, Charlotte Observer, 30 Mar. 2026
See All Example Sentences for underground
Adjective
The spa The 57-foot-long underground pool is a treasure.
—Condé Nast, Condé Nast Traveler, 3 Apr. 2026
Exhibitors include Nicola Bulgari, who keeps part of his vast car collection in an underground garage in central Rome, and sponsors include Swiss bank UBS, Gulfstream, Richard Mille, and RM Sotheby’s.
—Ben Oliver, Robb Report, 3 Apr. 2026
Noun
Engineers inject water to dissolve part of the salt, pump out the salty brine, and are left with an empty chamber underground.
—Rupendra Brahambhatt, Interesting Engineering, 22 Feb. 2026
Decades after that, when hoists fell silent in 1975, Bisbee’s underground ran for more than 2,000 miles on roughly 43 levels—a city folded beneath a town of just five square miles.
—Masha Hamilton, Longreads, 19 Feb. 2026
Adverb
The uranium itself may be hidden underground.
—Nancy A. Youssef, The Atlantic, 31 Mar. 2026
More broadly, the discovery highlights hidden biodiversity in groundwater systems and suggests older evolutionary lineages preserved underground.
—Hanna Wickes, Charlotte Observer, 30 Mar. 2026
See All Example Sentences for underground
Recent Examples of Synonyms for underground
Adjective
-
For decades, there’s been a quasi-clandestine accord about expanding oil drilling in the Gulf.—
Orlando Sentinel Editorial Board,
The Orlando Sentinel,
8 Apr. 2026
-
This clandestine supply chain eventually provided thousands of muskets, field artillery and millions of pounds of gunpowder that made possible the 1777 victory at Saratoga and France’s subsequent formal alliance.—
Christopher Magra,
The Conversation,
7 Apr. 2026
Adjective
-
Located between the Sahara tent and the Do Lab, the Bunker is a gigantic subterranean cavern with room for 300 or so people — a dark and cool respite from the blazing Indio sun.—
Mikael Wood,
Los Angeles Times,
10 Apr. 2026
-
The same poster, in pink and black this time, had been taped to the door of the subterranean gym.—
Sam Stone,
Bon Appetit Magazine,
9 Apr. 2026
Noun
-
Sometimes just surviving is an act of resistance and finding the grass that grows in the cracks in the asphalt.—
Sarah Lewin Frasier,
Scientific American,
10 Apr. 2026
-
When momentum faded, the stock rolled over, and those same lines flipped to resistance on the way down.—
Frank Cappelleri,
CNBC,
10 Apr. 2026
Adjective
-
Israeli air forces carrying out a strike on Tehran killed the commander of the Islamic Revolutionary Guard Corps' undercover expeditionary unit, the Israel Defense Forces said today.—
Max Burman,
NBC news,
6 Apr. 2026
-
Per the complaint, Gay admitted to engaging in text and Reddit conversations with the undercover account after being read his Miranda rights.—
Nick Lentz,
CBS News,
3 Apr. 2026
Adverb
-
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
-
While your portfolio grows over time, inflation is stealthily growing alongside it, eating away at the value of your savings.—
Ryan Ermey,
CNBC,
1 Apr. 2026
Adjective
-
That secret, a CNN investigation has found, centered on China’s covert plans to massively expand its nuclear ambitions.—
Tamara Qiblawi,
CNN Money,
1 Apr. 2026
-
Movies set in the world of top-secret spycraft and covert operations have entertained audiences for decades.—
Kevin Jacobsen,
Entertainment Weekly,
31 Mar. 2026
Adverb
-
Church members would pass them out surreptitiously for evangelism to prospective Iranian converts.—
Angie Leventis Lourgos,
Chicago Tribune,
4 Apr. 2026
-
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
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 12 Apr. 2026.
Copy CitationLove words? Need even more definitions?
Merriam-Webster unabridged
