adv., /un"deuhr grownd"/ ; adj., n., v. /un"deuhr grownd'/ , adv.
1. beneath the surface of the ground: traveling underground by subway.
2. in concealment or secrecy; not openly: subversion carried on underground.
adj.
3. existing, situated, operating, or taking place beneath the surface of the ground.
4. used, or for use, underground.
5. hidden or secret; not open: underground political activities.
6. published or produced by political or social radicals or nonconformists: an underground newspaper.
7. avant-garde; experimental: an underground movie.
8. critical of or attacking the established society or system: underground opinion.
9. of or for nonconformists; unusual: an underground vegetarian restaurant.
n.
10. the place or region beneath the surface of the ground.
11. an underground space or passage.
12. a secret organization fighting the established government or occupation forces: He fought in the French underground during the Nazi occupation of France.
13. ( often cap. ) a movement or group existing outside the establishment and usually reflecting unorthodox, avant-garde, or radical views.
14. Chiefly Brit. a subway system.
v.t.
15. to place beneath the surface of the ground: to underground utility lines.
[ 1565-75; UNDER- + GROUND 1 ]