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
Early evidence has shown the bombing did not reach depths necessary to destroy the facilities, which are buried deeply underground, according to a second U.S. official. Nicole Fallert, USA Today, 26 June 2025 The amount of groundwater replenishment during the 2024 water year, while significant, was less than the 8.7 million acre-feet that percolated underground during the extremely wet 2023 water year, according to state estimates. Ian James, Los Angeles Times, 24 June 2025
Noun
Turkmenistan possesses the world’s fourth largest reserves of natural gas in its underground, exporting gas to countries such as Pakistan, China, India, Iran and Russia. David Bressan, Forbes.com, 19 June 2025 New York is home to a thriving underground of edgy, experimental noise bands right now, and Brutus VIII, the conceptual project led by musician Jackson Katz, is one of the best. Simon Vozick-Levinson, Rolling Stone, 6 May 2025
Adjective
Israel has struck Natanz repeatedly and claims to have hurt its underground facilities, which experts assess contain 10,000 centrifuges that enrich uranium up to 60%. Natalie Melzer, Chicago Tribune, 17 June 2025 On June 13, Iran confirmed that Israel hit the Natanz nuclear facility, the country's main underground multi-level enrichment site. Amira El-Fekki‎, MSNBC Newsweek, 16 June 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 2 Jul. 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

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!