Underground
Underground , noun
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 , adjective
1.
Being below the surface of the ground; as, an underground story or apartment.
2.
Done or occurring out of sight; secret. [Colloquial]
Collocations (1)
Underground railroad or Underground railway , See under Railroad.
Underground , adverb
Beneath the surface of the earth.