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
Alphonse Pierre, Pitchfork, 22 May 2025
When the eggs hatch six weeks later, new cicada nymphs will fall from the trees and burrow back underground, starting the cycle again.
—Chris Simon, The Conversation, 22 May 2025
Andreas Wiseman, Deadline, 15 May 2025
However, remember that this will not remove the fungi underground, just the visible mushrooms.
—Arricca Elin Sansone, Southern Living, 11 May 2025
Claudia Alarcón, Forbes.com, 24 May 2025
The second phase of redevelopment is expected to double the size of the Stockyards, adding three hotels, 300,000 square feet of commercial space, at least 295 units of multifamily housing and two underground parking garages.
—Kate Marijolovic, Fort Worth Star-Telegram, 24 May 2025
See All Example Sentences for underground
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Adverb
Recently, New York drill has gone back underground, which is maybe where it was supposed to be all along.
—Alphonse Pierre, Pitchfork, 22 May 2025
When the eggs hatch six weeks later, new cicada nymphs will fall from the trees and burrow back underground, starting the cycle again.
—Chris Simon, The Conversation, 22 May 2025
Noun
The thriller follows a streetwise chess prodigy pulled into a brutal underground circuit where every match is a deadly gamble.
—Andreas Wiseman, Deadline, 15 May 2025
However, remember that this will not remove the fungi underground, just the visible mushrooms.
—Arricca Elin Sansone, Southern Living, 11 May 2025
Adjective
Weather permitting, chefs prepare cochinita pibil, perhaps the most iconic dish of the region, in an underground pit directly on the beach.
—Claudia Alarcón, Forbes.com, 24 May 2025
The second phase of redevelopment is expected to double the size of the Stockyards, adding three hotels, 300,000 square feet of commercial space, at least 295 units of multifamily housing and two underground parking garages.
—Kate Marijolovic, Fort Worth Star-Telegram, 24 May 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 May. 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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