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
Christina Coulter, PEOPLE, 22 Nov. 2025
Companies have developed various methods of keeping servers cool for optimal performance, from placing them deep underground where the temperature is naturally lower to running cold water through tubes connected to the chips, carrying heat away from the servers.
—Rachyl Jones, semafor.com, 21 Nov. 2025
Abby Price, Southern Living, 17 Nov. 2025
There was a kind of anti-Franco underground in Barcelona.
—John Hopewell, Variety, 11 Nov. 2025
Arkansas Online, 23 Nov. 2025
The feature, directed by Phil Giordano, follows Aya (Loisa Andalio), a young girl from Manila’s slums who dreams of becoming a billiards world champion but is manipulated by her hustler uncle Itoy, played by Arcilla, into playing dangerous underground gambling matches after her father’s murder.
—Naman Ramachandran, Variety, 23 Nov. 2025
See All Example Sentences for underground
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Adverb
Authorities believe most victims were strangled, but evidence is scant after years underground.
—Christina Coulter, PEOPLE, 22 Nov. 2025
Companies have developed various methods of keeping servers cool for optimal performance, from placing them deep underground where the temperature is naturally lower to running cold water through tubes connected to the chips, carrying heat away from the servers.
—Rachyl Jones, semafor.com, 21 Nov. 2025
Noun
Every detail, from the cozy underground setting to the authentic Belgian food and beer, perfectly captures the spirit of Europe.
—Abby Price, Southern Living, 17 Nov. 2025
There was a kind of anti-Franco underground in Barcelona.
—John Hopewell, Variety, 11 Nov. 2025
Adjective
Appearing before a congressional panel Thursday, Grace Jin Drexel said her father, Ezra Jin Mingri, was formally charged this past week along with 17 other leaders of the prominent underground Zion Church.
—Arkansas Online, 23 Nov. 2025
The feature, directed by Phil Giordano, follows Aya (Loisa Andalio), a young girl from Manila’s slums who dreams of becoming a billiards world champion but is manipulated by her hustler uncle Itoy, played by Arcilla, into playing dangerous underground gambling matches after her father’s murder.
—Naman Ramachandran, Variety, 23 Nov. 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 28 Nov. 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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