Underground /(?)/

Un·der·ground

Underground

n.
  1. The place or space beneath the surface of the ground; subterranean space.
    A spirit raised from depth of underground.
  2. a subway or subway system, especially in the United Kingdom. [chiefly British]
  3. a secret organization opposed to the prevailing government; as, the French underground during the Nazi occupation.
  4. a group or movement holding unorthodox views in an environment where conventional ideas dominate, as in artistic circles.

Underground

a.
  1. Being below the surface of the ground; as, an underground story or apartment.
  2. Done or occurring out of sight; secret. [Colloq.]

Phrases & Compounds
Underground railroad
See under Railroad.

Underground

adv.
  1. Beneath the surface of the earth.