• (Received Pronunciation) IPA^(key): /ˌʌn.dəˈɡɹaʊnd/, (especially for the noun) /ˈʌn.də.ɡɹaʊnd/

  • Audio (Southern England):

    (file)

• (General American) IPA^(key): /ˌʌn.dəɹˈɡɹaʊnd/, (especially for the noun) /ˈʌn.dəɹ.ɡɹaʊnd/
• Rhymes: -aʊnd
• Hyphenation: un‧der‧ground

From Middle English undergrounde (adverb), equivalent to under +‎ ground or under- +‎ ground. Compare Dutch ondergrond, ondergronds, German Untergrund, Danish undergrunds.

• under ground, under-ground (now rare)

underground (comparative more underground, superlative most underground)

1. (not comparable) Below the ground; below the surface of the Earth.

   Synonyms: subterranean, hypogean

   There is an underground tunnel that takes you across the river.

   • 2014 June 14, “It’s a gas”, in The Economist‎^[1], volume 411, number 8891, London: The Economist Group, →ISSN, →OCLC, archived from the original on 12 June 2014:

     One of the hidden glories of Victorian engineering is proper drains. Isolating a city’s effluent and shipping it away in underground sewers has probably saved more lives than any medical procedure except vaccination.

2. (figurative) Hidden, furtive, secretive.

   Synonyms: see Thesaurus:hidden, Thesaurus:covert

   These criminals operate through an underground network.

3. (figurative) Of or relating to an art forms (such as music) or subculture that is outside the mainstream, especially one that is unofficial and hidden from the authorities.

   Synonyms: alternative, unconventional

   Antonym: mainstream

   underground music

   • 1991, Stephen Fry, The Liar, page 27:

     ‘[…]he wrote to me last week telling me about an incredible bitch of a row blazing there on account of someone having been and gone and produced an unofficial magazine called Raddled, full of obscene libellous Oz-like filth. And what I though, what Sammy and I thought, was—why not?’ ‘Why not what?’ said Tom. ‘Why not do the same thing here?’ ‘You mean an underground magazine?’ ‘Yup.’

   • 2010 March 20, James Campbell, “Barry Miles: 'I think of the 60s as a supermarket of ideas. We were looking for new ways to live'”, in The Guardian‎^[2]:

     "In many ways, it showed there was no longer an underground, as such. This proved that there was no longer one society with everyone agreeing how to live . . . The underground had officially come above ground, and consequently no longer existed."

underground (comparative more underground, superlative most underground)

1. Below the ground.

   Synonym: below ground

   The tunnel goes underground at this point.

2. Secretly.

   Synonyms: clandestinely, in secret, on the quiet

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underground (plural undergrounds)

1. (geography) The regions beneath the surface of the earth, both natural (eg. caves) and man-made (eg. mines).
2. (chiefly British) Synonym of subway: a railway that is under the ground.

   Synonym: underground railway

   London Underground

3. (with definite article) A movement or organization of people who resist political convention.

   Synonym: resistance

   the French underground during World War II

   • 1942, Julius J. Epstein, Philip G. Epstein, Howard Koch, Casablanca, spoken by Ilsa (Ingrid Bergman):

     Victor, please, don't go to the underground meeting tonight.

4. (with definite article) A movement or organization of people who resist artistic convention.

   Synonyms: avant-garde, counterculture

underground (third-person singular simple present undergrounds, present participle undergrounding, simple past and past participle undergrounded)

1. To route electricity distribution cables underground.
   • 1962, David Pesonen, “Battles Over Energy”, in Carolyn Merchant, editor, Green Versus Gold: Sources in California's Environmental History‎^[3], Island Press, published 1998, →ISBN, page 325:

     One is to underground where no other alternative will work, and this method should be used universally in urban regions as it now is in “downtown” sections.

   • 2004, Don L. Ivey, C. Paul Scott, “Solutions”, in Transportation Research Board Committee on Utilities, editor, Utilities and Roadside Safety‎^[4], State of the Art Report 9, Transportation Research Board, →ISBN, page 9:

     Also, undergrounding may not eliminate the potential for crashes with other roadside objects, such as trees, walls, buildings, and so forth. [...] When looking at the fesibility of undergrounding utilities, the complete roadside area and nearby adjacent properties should be evaluated for potential roadside obstructions or hazards.

   • 2006, Janes Northcote-Green, Robert Wilson, “Design, Construction and Operation of Distribution Systems, MV Networks”, in Control and Automation of Electrical Power Distribution Systems‎^[5], CRC Press, →ISBN, page 110:

     The utility now wants the network to be undergrounded in the urban areas, which would mean substations with 33 kV distribution swtichgear.

See the etymology of the corresponding lemma form.

underground

1. simple past and past participle of undergrind

• “underground”, in Merriam-Webster.com Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.
• “underground”, in OneLook Dictionary Search.
• “underground, adj. & n.”, in OED Online 👁 Paid subscription required
  ⁠, Oxford: Oxford University Press, launched 2000.
• “underground, n.”, in OED Online 👁 Paid subscription required
  ⁠, Oxford: Oxford University Press, launched 2000.
• “underground, v.”, in OED Online 👁 Paid subscription required
  ⁠, Oxford: Oxford University Press, launched 2000.

Unadapted borrowing from English underground.

• IPA^(key): /ˈɑnder.ɡrɑund/, [ˈɑ̝nde̞rˌɡrɑ̝und]
• Rhymes: -ɑund

underground

1. underground (culture)

• “underground”, in Kielitoimiston sanakirja [Dictionary of Contemporary Finnish]‎^[6] (in Finnish) (online dictionary, continuously updated), Kotimaisten kielten keskuksen verkkojulkaisuja 35, Helsinki: Kotimaisten kielten tutkimuskeskus (Institute for the Languages of Finland), 2004–, retrieved 4 July 2023

Borrowed from English underground.

• IPA^(key): /œ̃.dɛʁ.ɡʁawnd/

underground (invariable)

1. underground (outside the mainstream)

underground m (uncountable)

1. (singular only) the underground (people who resist artistic convention)

• “underground”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012

Borrowed from English underground.

• IPA^(key): /an.derˈɡrawnd/^[1]
• Rhymes: -awnd

l'underground m (invariable)

1. the underground (people who resist artistic convention)

Unadapted borrowing from English underground.

underground m or f or n (indeclinable)

1. underground

Unadapted borrowing from English underground.

• IPA^(key): /andeɾˈɡɾaund/ [ãn̪.d̪eɾˈɣ̞ɾãũn̪d̪]
• IPA^(key): /ondeɾˈɡɾaund/ [õn̪.d̪eɾˈɣ̞ɾãũn̪d̪]
• Rhymes: -aund

underground m (plural undergrounds)

1. underground (movement)

According to Royal Spanish Academy (RAE) prescriptions, unadapted foreign words should be written in italics in a text printed in roman type, and vice versa, and in quotation marks in a manuscript text or when italics are not available. In practice, this RAE prescription is not always followed.

• “underground”, in Diccionario de la lengua española [Dictionary of the Spanish Language] (in Spanish), online version 23.8.1, Royal Spanish Academy [Spanish: Real Academia Española], 15 December 2025

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