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
Synonyms
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
Trilce Estrada Olvera, The Arizona Republic, 16 Aug. 2024
The water is believed to be hiding in the cracks of rocks underground and could be seven to 12 miles beneath the Martian crust.
—Greg Wehner, Fox News, 13 Aug. 2024
Oshan Jarow, Vox, 9 Aug. 2024
In telling the stories of Bonhoeffer and Dohnanyi, the book offers a fascinating portrait of the anti-Nazi underground.
—Peter Hoffmann, Foreign Affairs, 18 June 2014
Tresa Baldas, Detroit Free Press, 18 Aug. 2024
It’s helped that Southern California Edison’s lines are mostly underground and that the port, deemed a vital infrastructure, is exempt from brownouts, an outage resulting from a temporary drop in voltage.
—Don Lee, Los Angeles Times, 16 Aug. 2024
See all Example Sentences for underground 
Adverb
Her research suggests that activities such as uranium mining near the Grand Canyon are too dangerous since adjacent fault structures forming vertical conduits could rapidly transport water underground, finding its way down to the Redwall-Muav Aquifer.
—Trilce Estrada Olvera, The Arizona Republic, 16 Aug. 2024
The water is believed to be hiding in the cracks of rocks underground and could be seven to 12 miles beneath the Martian crust.
—Greg Wehner, Fox News, 13 Aug. 2024
Noun
And the psychedelic underground will continue providing access (for both better and worse) to those who manage to find it.
—Oshan Jarow, Vox, 9 Aug. 2024
In telling the stories of Bonhoeffer and Dohnanyi, the book offers a fascinating portrait of the anti-Nazi underground.
—Peter Hoffmann, Foreign Affairs, 18 June 2014
Adjective
According to its website and court records, Asphalt Specialists is a 25-year-old company of about 200 employees that provides numerous construction services, including asphalt paving, underground work and design.
—Tresa Baldas, Detroit Free Press, 18 Aug. 2024
It’s helped that Southern California Edison’s lines are mostly underground and that the port, deemed a vital infrastructure, is exempt from brownouts, an outage resulting from a temporary drop in voltage.
—Don Lee, Los Angeles Times, 16 Aug. 2024
See all Example Sentences for underground
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'underground.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
Dictionary Entries Near underground
Cite this Entry
“Underground.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/underground. Accessed 28 Aug. 2024.
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
Love words? Need even more definitions?
Merriam-Webster unabridged
Share