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

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

Etymology

Origin of underground

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

Example Sentences

It’s a vision wide enough to include monster trucks, lowriders, underground comedy, Miami street art, Texas barbecue and haggis tacos, dreamed up by Ferguson and executed by celebrity chef Marcus Samuelsson.

From Los Angeles Times • May 29, 2026

Dungannon Library had to close its doors earlier this month following significant flooding caused by issues within the underground drainage network.

From BBC • May 28, 2026

That means all the enriched uranium and the underground sites, with intrusive inspections and an enrichment ban.

From The Wall Street Journal • May 28, 2026

The insects were identified as Andrena regularis, commonly called the "regular mining bee," a solitary wild bee species that nests underground and helps pollinate crops and wild plants.

From Science Daily • May 28, 2026

Langer led everyone to an underground room, up to a table on which bulky shapes sat beneath a cloth.

From "The Bletchley Riddle" by Ruta Sepetys and Steve Sheinkin

Related Words

• clandestine
• experimental
• hidden
• private