underground

1 of 3

adverb

un·​der·​ground ˌən-dər-ˈgrau̇nd 

1

: beneath the surface of the earth

2

: in or into hiding or secret operation

underground

2 of 3

noun

ˈən-dər-ˌgrau̇nd 

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 

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

Noun

• resistance

Adjective

• backstairs
• behind-the-scenes
• clandestine
• covert
• furtive
• hole-and-corner
• hugger-mugger
• hush-hush
• private
• privy
• secret
• sneak
• sneaking
• sneaky
• stealth
• stealthy
• surreptitious
• undercover
• underhand
• underhanded

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

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

The company has amassed a war chest to lead the hunt for naturally-occurring hydrogen underground. —Katie Fehrenbacher, Axios, 15 Oct. 2024

Instead, Weilerstein seems to serve as part of the weird Mayan underground, with its mysterious gods and beasts. —Mark Swed, Los Angeles Times, 12 Oct. 2024

Adjective

Hezbollah leader Nasrallah was killed in an Israeli strike on his underground headquarters in Beirut in September. —Helen Regan, CNN, 26 Oct. 2024

This underground marvel spirals downwards, with walls lined with some of the world’s rarest wines, creating an enchanting display of history and luxury. —Rooksana Hossenally, Forbes, 26 Oct. 2024

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

Phrases Containing underground

• go underground
• the underground

Kids 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