📖 WordNook

underground

adverb
  1. beneath the surface of the earth
    “water flowing underground”
  2. in or into hiding or secret operation
    “the organization was driven underground”
adjective
  1. conducted with or marked by hidden aims or methods
    hugger-mugger
  2. under the level of the ground
    belowground
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'”
    metrotubesubway systemsubway
  2. a secret group organized to overthrow a government or occupation force
    resistance