a secret group organized to overthrow a government or occupation force

[ Syn: resistance ]

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

[ Syn: metro , tube , subway system , subway ]

in or into hiding or secret operation; the organization was driven underground'

beneath the surface of the earth; water flowing underground'

under the level of the ground; belowground storage areas; underground caverns

[ Syn: belowground ]

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

[ Syn: clandestine , cloak-and-dagger , hole-and-corner , hugger-mugger , hush-hush , secret , surreptitious , undercover ]