noun. a secret group organized to overthrow a government or occupation force |
noun. 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' |
adv. in or into hiding or secret operation the organization was driven underground |
adv. beneath the surface of the earth water flowing underground |
adj. under the level of the ground belowground storage areas|underground caverns |
adj. 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 |
