underground
Americanadverb
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beneath the surface of the ground.
traveling underground by subway.
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in concealment or secrecy; not openly.
subversion carried on underground.
adjective
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existing, situated, operating, or taking place beneath the surface of the ground.
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used, or for use, underground.
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hidden or secret; not open.
underground political activities.
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published or produced by political or social radicals or nonconformists.
an underground newspaper.
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avant-garde; experimental.
an underground movie.
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critical of or attacking the established society or system.
underground opinion.
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of or for nonconformists; unusual.
an underground vegetarian restaurant.
noun
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the place or region beneath the surface of the ground.
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an underground space or passage.
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a secret organization fighting the established government or occupation forces.
He fought in the French underground during the Nazi occupation of France.
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(often initial capital letter) a movement or group existing outside the establishment and usually reflecting unorthodox, avant-garde, or radical views.
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Chiefly British. a subway system.
verb (used with object)
adjective
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occurring, situated, or used below ground level
an underground tunnel
an underground explosion
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secret; hidden
underground activities
adverb
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going below ground level
the tunnel led underground
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into hiding or secrecy
the group was driven underground
noun
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a space or region below ground level
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a movement dedicated to overthrowing a government or occupation forces, as in the European countries occupied by the German army in World War II
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( as modifier )
an underground group
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US and Canadian equivalent: subway. an electric passenger railway operated in underground tunnels
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(usually preceded by the)
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any avant-garde, experimental, or subversive movement in popular art, films, music, etc
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( as modifier )
the underground press
underground music
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Etymology
Origin of underground
Vocabulary lists containing underground
Florida's B.E.S.T. Common Prefixes: under-
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Spelling Practice, Unit 1
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Essential Question Vocabulary (Unit 5)
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The broker notes that underground mining introduces extra execution and long-term cost risks.
From The Wall Street Journal • May 26, 2026
However, an underground development project also approved for Mt.
From The Wall Street Journal • May 26, 2026
When the alarms sound in the city, the two students no longer go to underground shelters, preferring a "good sleep" in the safety of basements.
From Barron's • May 25, 2026
"We have moved from operating in tents and open environments, to commercial buildings, to aircraft hangars, and now to underground locations," explained one commander during last week's exercise.
From BBC • May 24, 2026
He had dropped all pretense of questioning me on my underground activities and seemed especially to enjoy hearing about my childhood.
From "The Hiding Place" by Corrie ten Boom
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
