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
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
Zeynep Tufekci, The Mercury News, 25 Feb. 2025
At one point when working in the field, Groat and his team discovered an object buried underground.
—Carolyn Stein, Chicago Tribune, 21 Feb. 2025
Nina Corcoran, Pitchfork, 6 Feb. 2025
The toolkit was first put up for sale on a Russian criminal underground forum for $2,500 in Oct. 2024.
—Davey Winder, Forbes, 10 Feb. 2025
Evan Simko-Bednarski, New York Daily News, 15 Feb. 2025
Those underground punks went so hard that NBC was bombarded with complaints in real time, leading the network to cut away from the performance to a pre-recorded sketch.
—Shannon Carlin, TIME, 15 Feb. 2025
See All Example Sentences for underground
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Adverb
The entire operation runs almost solely on paper, each retirement file hand-processed by hundreds of workers in a limestone mine 230 feet underground who ferry pieces of paper between the caverns to put them in the right manila folder.
—Zeynep Tufekci, The Mercury News, 25 Feb. 2025
At one point when working in the field, Groat and his team discovered an object buried underground.
—Carolyn Stein, Chicago Tribune, 21 Feb. 2025
Noun
Formed in 1966 in Canterbury, Kent, Soft Machine made a name for themselves on the London underground circuit playing a jazzy take on psychedelic prog-rock that eventually earned them slots opening for Pink Floyd and, in the U.S., Jimi Hendrix.
—Nina Corcoran, Pitchfork, 6 Feb. 2025
The toolkit was first put up for sale on a Russian criminal underground forum for $2,500 in Oct. 2024.
—Davey Winder, Forbes, 10 Feb. 2025
Adjective
As previously reported by The News, the MTA has been struggling to fix a 2,000 foot underground pipe at the facility since 2021, when the line responsible for feeding the sprinkler system from the city main failed to hold pressure.
—Evan Simko-Bednarski, New York Daily News, 15 Feb. 2025
Those underground punks went so hard that NBC was bombarded with complaints in real time, leading the network to cut away from the performance to a pre-recorded sketch.
—Shannon Carlin, TIME, 15 Feb. 2025
See All Example Sentences for underground
Cite this Entry
“Underground.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/underground. Accessed 3 Mar. 2025.
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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