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
Tony Briscoe, Los Angeles Times, 22 Oct. 2024
The Israeli military says the bunker contains living quarters and amenities for extended stays, equipment for commanding Hezbollah members from underground, and a vast fortune.
—Timothy Nerozzi, Washington Examiner - Political News and Conservative Analysis About Congress, the President, and the Federal Government, 22 Oct. 2024
Brian Tallerico, Vulture, 16 Oct. 2024
The instruments lie more than a kilometer underground to avoid interference from cosmic rays and other sources of energy.
—Saima S. Iqbal, Scientific American, 4 Sep. 2024
Hernán Muñoz and Joseph Wilson, Los Angeles Times, 5 Nov. 2024
Security forces have been searching for victims in ravines and underground garages, including a large parking lot at the Bonaire shopping center in Aldaia.
—Atika Shubert, CNN, 4 Nov. 2024
See all Example Sentences for underground 
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Adverb
For this project, companies will need to capture, compress and transport CO2 underground — a process that requires a lot of energy and potentially could lead to more emissions.
—Tony Briscoe, Los Angeles Times, 22 Oct. 2024
The Israeli military says the bunker contains living quarters and amenities for extended stays, equipment for commanding Hezbollah members from underground, and a vast fortune.
—Timothy Nerozzi, Washington Examiner - Political News and Conservative Analysis About Congress, the President, and the Federal Government, 22 Oct. 2024
Noun
In this case, toxic masculinity gets merged with the urban legend of an underground that steals kidneys and leaves people in bathtubs.
—Brian Tallerico, Vulture, 16 Oct. 2024
The instruments lie more than a kilometer underground to avoid interference from cosmic rays and other sources of energy.
—Saima S. Iqbal, Scientific American, 4 Sep. 2024
Adjective
It is feared that inside some of the vehicles that were washed away or trapped in underground garages there could be bodies waiting to be recovered.
—Hernán Muñoz and Joseph Wilson, Los Angeles Times, 5 Nov. 2024
Security forces have been searching for victims in ravines and underground garages, including a large parking lot at the Bonaire shopping center in Aldaia.
—Atika Shubert, CNN, 4 Nov. 2024
See all Example Sentences for underground
Dictionary Entries Near underground
Cite this Entry
“Underground.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/underground. Accessed 16 Nov. 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
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