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REFERENCE

underground

adj. · adv. · n.
US //ˈəndɝˌɡɹaʊnd// un·der·ground
  1. 1 below the surface (adj.)
    A2 Elementary

    located or happening under the ground.

    situated, occurring, or operating below the surface of the earth.

    Example

    The hotel has an underground car park for its guests.

    Example

    The engineers discovered an extensive network of underground streams that complicated the foundation work for the new skyscraper.
  2. 2 alternative or secret (adj.)
    B2 Upper Intermediate

    secret or outside of the mainstream, often used for art, music, or politics.

    relating to a subculture or movement that is unofficial, non-mainstream, or hidden from authorities.

    Example

    He plays guitar in an underground rock band that only performs in small clubs.

    Example

    The underground press played a crucial role in distributing information during the years of strict government censorship.
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  1. 3 below the ground (adv.)
    A2 Elementary

    under the surface of the earth.

    below the surface of the ground; in or into a subterranean location.

    Example

    Rabbits live underground in tunnels called burrows.

    Example

    The utility company decided to move all the power lines underground to protect them from severe winter storms.
    • belowground
  2. 4 into hiding (adv.)
    B2 Upper Intermediate

    into a place or state of hiding to avoid being caught.

    into a state of secrecy or concealment, typically to evade observation or arrest.

    Example

    The political leader went underground after the police started looking for him.

    Example

    After the failed coup, the remaining activists went underground to reorganise their movement without fear of immediate detection.
  3. 5 train system (n.)
    A2 Elementary British English

    a railway system that runs under the ground in a city.

    an electric passenger railway system operating in tunnels beneath a city surface.

    Example

    It is much faster to take the underground than to drive through the city centre.

    Example

    The London Underground is the oldest subterranean railway network in the world, with some sections dating back to 1863.

    Usage

    Often used with the definite article 'the'.

    Teacher's tip

    In the UK, people say 'the Underground' or 'the Tube'; in the US, 'the subway' is the standard term.
  4. 6 resistance movement (n.)
    C1 Advanced Formal

    a secret group of people working together to fight against a government.

    a clandestine organisation or movement engaged in resisting an established government or occupying power.

    Example

    She joined the underground to help fight for her country's freedom.

    Example

    Members of the French underground risked their lives to gather intelligence and sabotage enemy supply lines during the occupation.

    Usage

    Usually used with the definite article 'the'.
Etymology 1

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

Etymology 2

See the etymology of the corresponding lemma form.

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