underground 1 of 3

adjective

ˈən-dər-ˌgrau̇nd How to pronounce underground (audio)
Definition of undergroundnext
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

underground

2 of 3

noun

ˈən-dər-ˌgrau̇nd How to pronounce underground (audio)
as in resistance
a secret organization in a conquered country fighting against enemy forces joined the underground while still a teenager

Synonyms & Similar Words

underground

3 of 3

adverb

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
Adjective
These underground networks reflect Afghans’ hopes for a better future. — Mark Sappenfield, Christian Science Monitor, 9 Oct. 2026 Jerusalem — The strike plan called for hitting a vast underground complex in Gaza’s southern city of Rafah, comprised of dozens of rooms and a network of interconnecting tunnels. — Jeremy Diamond, CNN Money, 8 Oct. 2026
Noun
Since the late 1990s, taxpayers have been funding a program to stash extra Colorado River water underground, with the idea that it could be used as a backup in times of shortage. — Alex Hager, NPR, 31 Aug. 2026 On Facebook, discussion groups foster the feeling of a countercultural underground. — Ruby Cramer, New Yorker, 31 Aug. 2026
Adverb
No one has yet stored a data center’s heat underground at that scale. — Moones Alamooti, The Conversation, 9 Oct. 2026 The infrastructure is buried underground, already doing its work for the citizens. — Doug Ross, Chicago Tribune, 8 Oct. 2026 See All Example Sentences for underground
Recent Examples of Synonyms for underground
  1. clandestine
  2. subterranean
  3. resistance
  4. stealthily
  5. undercover
  6. surreptitiously
  7. covert
  8. clandestinely
Adjective
  • Bridgers’ tour restricts phones, so the reader’s account had to stand in for the clandestine photo that might otherwise have accompanied the sighting.
    — Jeff Ihaza, Rolling Stone, 6 Oct. 2026
  • The Soviet Union operated an extensive clandestine biological weapons program despite being a party to the Biological Weapons Convention.
    — Krutika Kuppalli, STAT, 6 Oct. 2026
Definition of clandestine
Adjective
  • The atmosphere is dark and subterranean, a Batcave of wellness.
    — Condé Nast, Condé Nast Traveler, 10 Oct. 2026
  • However, the price does account for an 875-square-foot subterranean addition installed in 2021, as well as a pool and cabin tacked onto the land in 2020.
    — Wendy Bowman, Robb Report, 9 Oct. 2026
Definition of subterranean
Noun
  • Slota’s stated contempt for law enforcement and support for armed resistance was on display before his arrest.
    — Hudson Crozier, The Washington Examiner, 9 Oct. 2026
  • Through their grief and persistence, the film explores memory, resistance and a wound left open by institutional neglect.
    — Anna Marie de la Fuente, Variety, 9 Oct. 2026
Definition of resistance
Adverb
  • The spread of the video was aided by clippers, accounts that post hundreds of clips in a single day and are paid by companies to stealthily link these viral moments to their platforms.
    — CT Jones, Rolling Stone, 11 Sep. 2026
  • Wolf’s Shinobi Prosthetic houses a grappling hook for scaling rooftops, leaping between trees, and approaching enemies stealthily.
    — Aman Kumar, Encyclopedia Britannica, 27 Aug. 2026
Definition of stealthily
Adjective
  • The show revolved around Crockett and Tubbs, two undercover detectives infiltrating South Florida’s criminal underworld.
    — Matt Grobar, Deadline, 13 Oct. 2026
  • At its center is a youngish man named Bob Arctor, an undercover cop who starts using drugs in order to infiltrate a house full of addicts in Southern California.
    — Hilton Als, New Yorker, 12 Oct. 2026
Definition of undercover
Adverb
  • Among the most intriguing possibilities, Brouhard said, is that Gulf nations exporting oil are surreptitiously paying Iran fees in exchange for safe transit through the Strait of Hormuz – even as they’re secured by US military escorts.
    — David Goldman, CNN Money, 6 Oct. 2026
  • In the first image above, Wardle can be seen using a simple terminal command to surreptitiously send a prompt to the Meta endpoint.
    — Dan Goodin, ArsTechnica, 21 Sep. 2026
Definition of surreptitiously
Adjective
  • There has been serious buzz recently about the film series focused on the United States conducting covert actions against drug cartels.
    — David Hookstead OutKick, FOXNews.com, 6 Oct. 2026
  • Flashbacks to recent events reveal that the townspeople never let Hal find peace, and even firebombed his home, only for a grown-up Noah — Kerry’s son, and Zoe’s grandson — to save him and regenerate his skin using Zoe’s covert alien tech.
    — Siddhant Adlakha, Vulture, 5 Oct. 2026
Definition of covert
Adverb
  • Because Iran is a theocratic dictatorship that routinely arrests and in some cases executes journalists, Western reporters hoping to cover the country must either work clandestinely or submit to government supervision.
    — James Kirchick, The Atlantic, 29 July 2026
  • Soon afterward, social media commenters were speculating about whether Sierra broke into the office or was caught clandestinely shredding documents.
    — Don Stacom, Hartford Courant, 10 July 2026
Definition of clandestinely

Browse Nearby Words

undergraduates
underground
undergrounds
See all Nearby Words

Cite this Entry

“Underground.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/underground. Accessed 15 Oct. 2026.

Copy Citation

More from Merriam-Webster on underground

Britannica.com: Encyclopedia article about underground

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Last Updated: - Updated example sentences

More from Merriam-Webster

Word of the Day

Listen to the pronunciation of outlandish

See Definitions and Examples »

Popular in Grammar & Usage

See More

'Affect' vs. 'Effect'

Merriam-Webster’s Great Big List of Words You Love to Hate

The Exceptions of '-s' and '-es' Plurals

Is it 'nerve-racking' or 'nerve-wracking'?

What's the difference between 'fascism' and 'socialism'?
See More

Popular in Wordplay

See More

16 Food Words Recently Added to the Dictionary

The Real Origin of 'Supercalifragilistic'

9 Words That Sound Like Insults But Aren't

7 Words for Bad Endings and Rough Situations

The Words of the Week - Oct. 9
See More

Popular

See More

'Affect' vs. 'Effect'

16 Food Words Recently Added to the Dictionary

The Real Origin of 'Supercalifragilistic'
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
The Missing Letter A daily crossword with a twist
a cup of tea and a golf ball on tee side by side
Quiz: Sounds Like... Choose the word that sounds like it fits the clue...
See All