un·der·ground
ˌən-dər-ˈgrau̇nd 
1
: beneath the surface of the earth
2
: in or into hiding or secret operation
1
: a subterranean space or channel
2
: an underground city railway system
3
a
: a movement or group organized in strict secrecy among citizens especially in an occupied country for maintaining communications, popular solidarity, and concerted resistive action pending liberation
b
: a clandestine conspiratorial organization set up for revolutionary or other disruptive purposes especially against a civil order
c
: an unofficial, unsanctioned, or illegal but informal movement or group
especially
: a usually avant-garde group or movement that functions outside the establishment
un·der·ground
ˈən-dər-ˌgrau̇nd
1
: being, growing, operating, or situated below the surface of the ground
2
: conducted by secret means
3
a
: existing outside the establishment
an underground literary reputation
b
: existing outside the purview of tax collectors or statisticians
the underground economy
4
a
: produced or published outside the establishment especially by the avant-garde
underground movies
underground newspapers
b
: of or relating to the avant-garde underground
an underground moviemaker
an underground theater
Synonyms
Examples of underground in a Sentence
Adverb
They had been living underground as fugitives.
Noun
I've ridden on the New York subway, the Paris Metro, and the London Underground.
joined the underground while still a teenager
Adjective
The drugs are supplied through an underground network.
She loves the city's underground music scene.
Recent Examples on the Web
Jenna Prestininzi, Detroit Free Press, 24 Apr. 2024
The third reservoir is located underground near 96th Street and Mitchell Street and has a capacity of 4 million gallons.
—Adrienne Davis, Journal Sentinel, 18 Apr. 2024
Two different broods of cicadas — Brood XIX, which lives on a 13-year cycle, and Brood XIII, which lives on a 17-year cycle — will emerge at the same time from underground for the first time since 1803.
—Elizabeth Robinson, NBC News, 12 Apr. 2024
In the past, researchers have tried to learn more about southern marsupial moles by placing microphones underground.
—Sarah Kuta, Smithsonian Magazine, 11 Apr. 2024
The length of time spent underground can vary depending on the species and environmental factors and is typically several years.
—The Arizona Republic, 11 Apr. 2024
Surfacing only after such long gaps and doing so in such vast numbers ensures that although they are easily preyed upon by other animals, plenty will survive to spawn a new population to return underground for the next 13 or 17 years.
—Andy Fies, ABC News, 7 Apr. 2024
As for the original Beal experiment, four bottles remain underground, waiting to be studied.
—Kate Golembiewski, Discover Magazine, 5 Apr. 2024
These types of volcanic bursts are probably caused by volatiles underground, experts say.
—Shi En Kim, Smithsonian Magazine, 16 Apr. 2024
Jane C. Hu, The Atlantic, 8 Apr. 2024
More:Pontiac home that went viral for $1 listing goes through renovations, sells for $140,000
The mansion has all new windows, new tile roof and copper gutters, all new electrical, plumbing and gas underground services prepped to be brought into the house, reads the real estate listing description.
—Brendel Hightower, Detroit Free Press, 14 Mar. 2024
Desperate to hire a bouncer, Frankie finds her man in Elwood Dalton (Gyllenhaal), a former pro fighter who now earns cash in a seedy underground fighting ring.
—Devan Coggan, EW.com, 21 Mar. 2024
Farrell gives a classic gangster monologue throughout the trailer, which slowly ramps up the violence and gunfights in Gotham City’s seedy underground.
—Caroline Brew, Variety, 22 Mar. 2024
Rather than targeting big corporations, the hackers in India’s underground are routinely paid to access personal email accounts, whether by a wife spying on her husband’s financial affairs or a blackmail victim searching for a way out of their predicament.
—Chris Wheatley, Longreads, 12 Mar. 2024
Of course, one of the main challenges remains simply digging deep enough into the Earth’s crust to tap the staggering amount of geothermal energy underground.
—IEEE Spectrum, 12 Mar. 2024
These actions have often been accompanied by sanctions and indictments for key members of the cybercrime underground.
—Matt Burgess, WIRED, 20 Feb. 2024
It is seen most clearly in rising rap, where the online underground encompasses a diffuse sprawl of scenes and standards that share a cracked sensibility.
—Kieran Press-Reynolds, Pitchfork, 19 Jan. 2024
Alessandro Corona, The Enquirer, 18 Apr. 2024
While the Eilish appearance, which was announced via social media just an hour beforehand, became another high-profile event at Coachella, the Do LaB stage is less about big names than a mission to bring a bit of underground culture to Indio.
—Steve Appleford, SPIN, 18 Apr. 2024
The water is supplied through two meter points and is then distributed to locations in the city through a maze of underground transmission and distribution mains and three reservoirs.
—Adrienne Davis, Journal Sentinel, 18 Apr. 2024
The female will then carry a cicada back to her underground nest, where the paralyzed cicada will remain alive while the wasp larvae feed.
—Emily Deletter, USA TODAY, 17 Apr. 2024
The film takes place in the Atacama desert, where Pacífico runs an underground mining endeavor.
—Holly Jones, Variety, 17 Apr. 2024
Some researchers think that the volatiles came from underground relatively recently, while others think the chemicals have persisted on the surface since an embryonic Mercury condensed from its protoplanetary disk.
—Shi En Kim, Smithsonian Magazine, 16 Apr. 2024
The two began working together, seeking to apply Moreno’s abstract techniques to the Jupiter-Europa system and to Saturn and its moon Enceladus, which, like Europa, might have life in its underground ocean.
—Quanta Magazine, 15 Apr. 2024
The showpiece here is the 85-foot indoor lap pool, set in an underground chamber with lighting designed to mimic daylight.
—Stacey Wreathall, Travel + Leisure, 6 Apr. 2024
Adverb
Typically active from summer to fall, females tend to be solitary and make nests underground, while males often sleep in clusters, sometimes on flowers.
—Jenna Prestininzi, Detroit Free Press, 24 Apr. 2024
The third reservoir is located underground near 96th Street and Mitchell Street and has a capacity of 4 million gallons.
—Adrienne Davis, Journal Sentinel, 18 Apr. 2024
Two different broods of cicadas — Brood XIX, which lives on a 13-year cycle, and Brood XIII, which lives on a 17-year cycle — will emerge at the same time from underground for the first time since 1803.
—Elizabeth Robinson, NBC News, 12 Apr. 2024
In the past, researchers have tried to learn more about southern marsupial moles by placing microphones underground.
—Sarah Kuta, Smithsonian Magazine, 11 Apr. 2024
The length of time spent underground can vary depending on the species and environmental factors and is typically several years.
—The Arizona Republic, 11 Apr. 2024
Surfacing only after such long gaps and doing so in such vast numbers ensures that although they are easily preyed upon by other animals, plenty will survive to spawn a new population to return underground for the next 13 or 17 years.
—Andy Fies, ABC News, 7 Apr. 2024
As for the original Beal experiment, four bottles remain underground, waiting to be studied.
—Kate Golembiewski, Discover Magazine, 5 Apr. 2024
These types of volcanic bursts are probably caused by volatiles underground, experts say.
—Shi En Kim, Smithsonian Magazine, 16 Apr. 2024
Noun
Because legal weed is sometimes more expensive than old-school dealer prices, plenty of people simply stick with the unregulated underground.
—Jane C. Hu, The Atlantic, 8 Apr. 2024
More:Pontiac home that went viral for $1 listing goes through renovations, sells for $140,000
The mansion has all new windows, new tile roof and copper gutters, all new electrical, plumbing and gas underground services prepped to be brought into the house, reads the real estate listing description.
—Brendel Hightower, Detroit Free Press, 14 Mar. 2024
Desperate to hire a bouncer, Frankie finds her man in Elwood Dalton (Gyllenhaal), a former pro fighter who now earns cash in a seedy underground fighting ring.
—Devan Coggan, EW.com, 21 Mar. 2024
Farrell gives a classic gangster monologue throughout the trailer, which slowly ramps up the violence and gunfights in Gotham City’s seedy underground.
—Caroline Brew, Variety, 22 Mar. 2024
Rather than targeting big corporations, the hackers in India’s underground are routinely paid to access personal email accounts, whether by a wife spying on her husband’s financial affairs or a blackmail victim searching for a way out of their predicament.
—Chris Wheatley, Longreads, 12 Mar. 2024
Of course, one of the main challenges remains simply digging deep enough into the Earth’s crust to tap the staggering amount of geothermal energy underground.
—IEEE Spectrum, 12 Mar. 2024
These actions have often been accompanied by sanctions and indictments for key members of the cybercrime underground.
—Matt Burgess, WIRED, 20 Feb. 2024
It is seen most clearly in rising rap, where the online underground encompasses a diffuse sprawl of scenes and standards that share a cracked sensibility.
—Kieran Press-Reynolds, Pitchfork, 19 Jan. 2024
Adjective
There's a very healthy underground movement of young artists that are just hitting the scene that are doing incredible things on the guitar.
—Alessandro Corona, The Enquirer, 18 Apr. 2024
While the Eilish appearance, which was announced via social media just an hour beforehand, became another high-profile event at Coachella, the Do LaB stage is less about big names than a mission to bring a bit of underground culture to Indio.
—Steve Appleford, SPIN, 18 Apr. 2024
The water is supplied through two meter points and is then distributed to locations in the city through a maze of underground transmission and distribution mains and three reservoirs.
—Adrienne Davis, Journal Sentinel, 18 Apr. 2024
The female will then carry a cicada back to her underground nest, where the paralyzed cicada will remain alive while the wasp larvae feed.
—Emily Deletter, USA TODAY, 17 Apr. 2024
The film takes place in the Atacama desert, where Pacífico runs an underground mining endeavor.
—Holly Jones, Variety, 17 Apr. 2024
Some researchers think that the volatiles came from underground relatively recently, while others think the chemicals have persisted on the surface since an embryonic Mercury condensed from its protoplanetary disk.
—Shi En Kim, Smithsonian Magazine, 16 Apr. 2024
The two began working together, seeking to apply Moreno’s abstract techniques to the Jupiter-Europa system and to Saturn and its moon Enceladus, which, like Europa, might have life in its underground ocean.
—Quanta Magazine, 15 Apr. 2024
The showpiece here is the 85-foot indoor lap pool, set in an underground chamber with lighting designed to mimic daylight.
—Stacey Wreathall, Travel + Leisure, 6 Apr. 2024
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'underground.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
Dictionary Entries Near underground
Cite this Entry
“Underground.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/underground. Accessed 2 May. 2024.
Copy CitationKids Definition
underground
1 of 3 adverb
un·der·ground
ˌən-dər-ˈgrau̇nd
1
: below the surface of the ground
an underground passage
2
: in or into hiding or secret operation
the political party went underground
underground
2 of 3 noun
un·der·ground
ˈən-dər-ˌgrau̇nd
1
: a space under the surface of the ground
especially
: subway sense 2
2
: a secret political group
especially
: an organized body working in secret to overthrow a government or an occupying power
underground
3 of 3 adjective
un·der·ground
ˈən-dər-ˌgrau̇nd
1
: being, growing, operating, or located below the surface of the ground
an underground stream
2
: conducted secretly
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