underground

American  

[uhn-der-ground, uhn-der-ground] / ˈʌn dərˈgraʊnd, ˈʌn dərˌgraʊnd /

adverb

1. beneath the surface of the ground.

   traveling underground by subway.

2. in concealment or secrecy; not openly.

   subversion carried on underground.

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adjective

1. existing, situated, operating, or taking place beneath the surface of the ground.

2. used, or for use, underground.

3. hidden or secret; not open.

   underground political activities.

4. published or produced by political or social radicals or nonconformists.

   an underground newspaper.

5. avant-garde; experimental.

   an underground movie.

6. critical of or attacking the established society or system.

   underground opinion.

7. of or for nonconformists; unusual.

   an underground vegetarian restaurant.

noun

undergrounds plural

1. the place or region beneath the surface of the ground.

2. an underground space or passage.

3. a secret organization fighting the established government or occupation forces.

   He fought in the French underground during the Nazi occupation of France.

4. (often initial capital letter) a movement or group existing outside the establishment and usually reflecting unorthodox, avant-garde, or radical views.

5. Chiefly British. a subway system.

verb (used with object)

1. to place beneath the surface of the ground.

   to underground utility lines.

underground British  

adjective

1. occurring, situated, or used below ground level

   an underground tunnel

   an underground explosion

2. secret; hidden

   underground activities

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adverb

1. going below ground level

   the tunnel led underground

2. into hiding or secrecy

   the group was driven underground

noun

1. a space or region below ground level

2. 1. a movement dedicated to overthrowing a government or occupation forces, as in the European countries occupied by the German army in World War II

   2. ( as modifier )

      an underground group

3. US and Canadian equivalent: subway.  an electric passenger railway operated in underground tunnels

4. (usually preceded by the)

   1. any avant-garde, experimental, or subversive movement in popular art, films, music, etc

   2. ( as modifier )

      the underground press

      underground music

Other Word Forms

Noun Inflected Forms

• undergrounds
  plural

Etymology

Origin of underground

First recorded in 1565–75; under- + ground ¹

Example Sentences

He said he gets transported back to his childhood when he goes in, "memories of walking around with a torch with hardly any batteries, getting lost underground".

From BBC • Jul. 11, 2026

The 30-inch steel pipeline runs underground from Cadiz’s desert property, near the town of Amboy, northward to the town of Mojave.

From Los Angeles Times • Jul. 10, 2026

Gas in underground storage facilities rose by 61 billion cubic feet to 2,983 Bcf, expanding the surplus to 185 Bcf from 175 Bcf the week before.

From The Wall Street Journal • Jul. 9, 2026

Through more than four years of the Russian invasion, 27-year-old Oleksiy Virskovsky largely hasn't bothered going to the underground shelter in the building next door -- despite almost nightly missile and drone attacks.

From Barron's • Jul. 9, 2026

Autumn, Ama, Woo, and I go tumbling down, into the underground … into an even deeper level of Asamando.

From "Kwame Crashes the Underworld" by Craig Kofi Farmer

Related Words

• clandestine
• experimental
• hidden
• private