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underground

/ˌʌn.dəɹˈɡɹaʊnd/noun, adjective, adverb3 syllables

Underground means: conducted with or marked by hidden aims or methods.

Synonyms for underground31

noun, as in an electric railway operating below the surface of the ground (usually in a city)

metro, tube, subway system, subway

noun, as in a secret group organized to overthrow a government or occupation force

resistance

adjective, as in conducted with or marked by hidden aims or methods

clandestine, cloak-and-dagger, hole-and-corner, hugger-mugger, hush-hush, secret, surreptitious, undercover, covert

adjective, as in under the level of the ground

belowground, subsurface

also used for underground

subterranean, hypogean, covered, concealed, dark, dern, hidden, invisible, inward, latent, nondisplayed, obfuscated, alternative, unconventional, below ground

Includes material from Wiktionary, CC BY-SA 4.0.

What does underground mean?6

adjective

1

conducted with or marked by hidden aims or methods“clandestine intelligence operations”

2

under the level of the ground“belowground storage areas”

noun

1

an electric railway operating below the surface of the ground (usually in a city)“in Paris the subway system is called the ‘metro’ and in London it is called the ‘tube’ or the ‘underground’”

2

a secret group organized to overthrow a government or occupation force

adverb

1

in or into hiding or secret operation“the organization was driven underground”

2

beneath the surface of the earth“water flowing underground”

Definitions from the Open English WordNet, CC BY 4.0.

Underground in a sentence

  • Go on the underground, and you'll get to hospital quicker.sundown
  • Which is quicker, a taxi or the underground?sundown
  • Is it possible that an enormous underground city exists, as yet undiscovered by anyone?adamtrousers
  • The collier spent his days deep underground, mining coal in dangerous conditions.rul
  • In the underground, to double-cross any member means sure death.unknown
  • When the hare realised the fox had gone, it emerged from its underground dwelling.sundown
  • Would you show me to the nearest underground station, please?yessoos
  • There are many kinds of burrowing animals, who make their homes underground.evan10593

Sentences from Tatoeba, CC BY 2.0 FR, credited to their authors.

Forms of underground

as a noun

plural
undergrounds