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
Shi En Kim, Smithsonian Magazine, 16 Apr. 2024
Snufkin himself, meanwhile, is famously based on Atos Wirtanen, a mercurial intellectual and one of Jansson’s lovers who spent much of his life opposing the rise of Nazism and the Finnish far right, having to briefly live underground due to his then-radical beliefs.
—Laurence Russell, WIRED, 16 Apr. 2024
Read Next ‘Ghostly’ creature — named after Harry Potter villain — discovered underground.
—Irene Wright, Miami Herald, 16 Apr. 2024
The coastal aquifer is depleted; the water underground is brackish without treatment.
—Keith Gessen, The New Yorker, 13 Apr. 2024
The two broods will begin to emerge when the soil 8 inches underground reaches 64 degrees, and are often triggered by a warm rain.
—Emily Deletter, USA TODAY, 13 Apr. 2024
The punk underground is represented by Jon Moritsugu, Sarah Jacobson and Dave Markey.
—Mark Olsen, Los Angeles Times, 12 Apr. 2024
The insects, which have been living underground for more than a decade, begin to dig upwards when the soil temperature reaches around 64 degrees Fahrenheit or more.
—Solcyré Burga, TIME, 12 Apr. 2024
Their front legs are often modified for digging, as nymphs spend much of their lives underground.
—The Arizona Republic, 11 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
These types of volcanic bursts are probably caused by volatiles underground, experts say.
—Shi En Kim, Smithsonian Magazine, 16 Apr. 2024
Snufkin himself, meanwhile, is famously based on Atos Wirtanen, a mercurial intellectual and one of Jansson’s lovers who spent much of his life opposing the rise of Nazism and the Finnish far right, having to briefly live underground due to his then-radical beliefs.
—Laurence Russell, WIRED, 16 Apr. 2024
Read Next ‘Ghostly’ creature — named after Harry Potter villain — discovered underground.
—Irene Wright, Miami Herald, 16 Apr. 2024
The coastal aquifer is depleted; the water underground is brackish without treatment.
—Keith Gessen, The New Yorker, 13 Apr. 2024
The two broods will begin to emerge when the soil 8 inches underground reaches 64 degrees, and are often triggered by a warm rain.
—Emily Deletter, USA TODAY, 13 Apr. 2024
The punk underground is represented by Jon Moritsugu, Sarah Jacobson and Dave Markey.
—Mark Olsen, Los Angeles Times, 12 Apr. 2024
The insects, which have been living underground for more than a decade, begin to dig upwards when the soil temperature reaches around 64 degrees Fahrenheit or more.
—Solcyré Burga, TIME, 12 Apr. 2024
Their front legs are often modified for digging, as nymphs spend much of their lives underground.
—The Arizona Republic, 11 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 25 Apr. 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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