English to English
1. Being below the surface of the ground; as, an underground story or apartment.
2. under the level of the ground
belowground storage areas|underground caverns
3. conducted with or marked by hidden aims or methods
clandestine intelligence operations|cloak-and-dagger activities behind enemy lines|hole-and-corner intrigue|secret missions|a secret agent|secret sales of arms|surreptitious mobilization of troops|an undercover investigation|underground resistance
4. in or into hiding or secret operation
the organization was driven underground
5. beneath the surface of the earth
water flowing underground
6. Beneath the surface of the earth.
7. a secret group organized to overthrow a government or occupation force
8. 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'
9. The place or space beneath the surface of the ground; subterranean space.