- beneath the surface of the ground: traveling underground by subway.
- in concealment or secrecy; not openly: subversion carried on underground.
- existing, situated, operating, or taking place beneath the surface of the ground.
- used, or for use, underground.
- hidden or secret; not open: underground political activities.
- published or produced by political or social radicals or nonconformists: an underground newspaper.
- avant-garde; experimental: an underground movie.
- critical of or attacking the established society or system: underground opinion.
- of or for nonconformists; unusual: an underground vegetarian restaurant.
- the place or region beneath the surface of the ground.
- an underground space or passage.
- a secret organization fighting the established government or occupation forces: He fought in the French underground during the Nazi occupation of France.
- a movement or group existing outside the establishment and usually reflecting unorthodox, avant-garde, or radical views.
- a subway system.
- to place beneath the surface of the ground: to underground utility lines.
- occurring, situated, or used below ground level
- secret; hidden
- going below ground level
- into hiding or secrecy
- a space or region below ground level
- a movement dedicated to overthrowing a government or occupation forces, as in the European countries occupied by the German army in World War II
- (as modifier)
- an electric passenger railway operated in underground tunnels
- (usually preceded by the)
- any avant-garde, experimental, or subversive movement in popular art, films, music, etc
- (as modifier)
