underground

1 of 3

adverb

un·​der·​ground ˌən-dər-ˈgrau̇nd How to pronounce underground (audio)
1
: beneath the surface of the earth
2
: in or into hiding or secret operation

underground

2 of 3

noun

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

underground

3 of 3

adjective

un·​der·​ground ˈən-dər-ˌgrau̇nd How to pronounce underground (audio)
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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Adverb
Pastors preached about the dangers and sacrifices miners faced deep underground, in an age of few regulations. The Conversation, 7 Oct. 2025 Once removed, planet-warming CO2 can be stored underground or used in industrial materials like cement. Ella Nilsen, CNN Money, 7 Oct. 2025
Noun
Unlike the neo-Leninist underground, moreover, dissidents had no desire to revive Bolshevik revolutionary traditions, with their ideological discipline, armed conspiracy, and noms de guerre. Benjamin Nathans september 24, Literary Hub, 24 Sep. 2025 Burnham Yard also is near an Environmental Protection Agency Superfund site for radium contamination, but the Terracon report did not find any indication that there is a substantial amount of radioactive material underground. Elliott Wenzler, Denver Post, 14 Sep. 2025
Adjective
About a decade ago, amid Syria's civil war, volunteers built a small, underground amusement park so little ones could play, shielded from bombing and shelling. Juliana Kim, NPR, 5 Oct. 2025 More than 200 pits have already been identified on the moon’s surface, and in 2024, NASA confirmed the presence of a large underground cavity. Christopher McFadden, Interesting Engineering, 5 Oct. 2025 See All Example Sentences for underground

Word History

First Known Use

Adverb

14th century, in the meaning defined at sense 1

Noun

1594, in the meaning defined at sense 1

Adjective

1601, in the meaning defined at sense 1

Time Traveler
The first known use of underground was in the 14th century

Browse Nearby Words

Cite this Entry

“Underground.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/underground. Accessed 10 Oct. 2025.

Kids Definition

underground

1 of 3 adverb
un·​der·​ground ˌən-dər-ˈgrau̇nd How to pronounce underground (audio)
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 How to pronounce underground (audio)
1
: being, growing, operating, or located below the surface of the ground
an underground stream
2
: conducted secretly

More from Merriam-Webster on underground

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