- (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.
- anchor hidden (figurative) Hidden, furtive, secretive.
- Synonyms: Thesaurus:hidden, Thesaurus:covert
- These criminals operate through an underground network.
- (Of music, art &c.) Outside the mainstream, especially unofficial and hidden from the authorities.
- Synonyms: unconventional, alternative
- Antonyms: mainstream
- underground music
- French: souterrain
- German: unterirdisch, Untergrund
- Italian: sotterraneo
- Portuguese: subterrâneo
- Russian: подзе́мный
- Spanish: subterráneo
- French: souterrain, clandestin
- German: heimlich, geheim, Untergrund
- Italian: clandestino
- Portuguese: clandestino, secreto
- Russian: подпо́льный
- Below the ground.
- Synonyms: clandestinely, in secret, on the quiet
- French: sous terre, sous la terre
- German: unter der Erde, unterirdisch
- Italian: sottoterra
- Russian: под земля
underground (plural undergrounds)
- (geography) Regions beneath the surface of the earth, both natural (eg. caves) and man-made (eg. mines).
- (chiefly, British) Synonym of subway#English|subway: a railway that is under the ground.
- London Underground
- (with definite article) A movement or organisation of people who resist political convention.
- Synonyms: resistance
- the French underground during World War II
- (with definite article) A movement or organisation of people who resist artistic convention.
- Synonyms: avant-garde, counterculture
- French: résistance, mouvement clandestin, organisation clandestine
- German: Untergrundorganisation
- Italian: resistenza, movimento clandestino, organizzazione clandestina
- Portuguese: resistência
- Russian: подпо́лье
- Spanish: movimiento clandestino, organización clandestina
- French: underground, mouvement d'avant-garde
- German: Underground
- Italian: underground
- Portuguese: submundo
- Russian: андергра́унд
underground (undergrounds, present participle undergrounding; past and past participle undergrounded)
- To route electricity distribution cables underground
- (UK, rail transport) The London Underground.
- Synonyms: Tube