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

Tips For Transplanting Make sure to provide the tomato seedlings ample room underground to establish roots and spread out. —Lauren David, Southern Living, 23 Mar. 2025

It was pushed back by Congolese forces and U.N. peacekeepers and forced underground in the province of North Kivu. —Emmet Livingstone, The Dial, 20 Mar. 2025

Noun

Salt water from the ocean or underground is rich in minerals and may provide the body with magnesium. —Susan Bard, Health, 18 Mar. 2025

The property would include 36 parking spaces — 22 surface-level and 14 underground. —Joe Marusak, Charlotte Observer, 17 Mar. 2025

Adjective

This week, Alphonse grapples with the yearning for the 2000s in UK underground rap videos. —Alphonse Pierre, Pitchfork, 21 Mar. 2025

Trending Video Margot Robbie Takes You Inside The Barbie Dreamhouse Despite the clever solutions for natural light underground, structural challenges loomed large. —Kristen Flanagan, Architectural Digest, 19 Mar. 2025

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

Rhymes for underground

• aboveground
• battleground
• belowground
• paperbound
• turnaround
• ultrasound
• wraparound
• abound
• aground
• around
• astound
• background

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