undergrounds

/AH1 N D ER0 G R AW0 N D Z/
noun
  1. 1

    An underground railway, especially for mass transit of people in urban areas.

  2. 2

    A train that runs on such an underground railway.

  3. 3

    A rapid transit system, regardless of the elevation of its right of way.

  4. 4

    An underground walkway, tunnel for pedestrians (called pedestrian underpass in US).

  5. 5

    An underground route for pipes, sewers, etc.

noun
  1. 1

    Regions beneath the surface of the earth, both natural (eg. caves) and man-made (eg. mines).

  2. 2

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

    โ€œthe French underground during World War IIโ€

  3. 3

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

verb
  1. 1

    To route electricity distribution cables underground

Source: https://en.wiktionary.org/wiki/subway, https://en.wiktionary.org/wiki/underground, https://en.wiktionary.org/wiki/undergrounds