· a secret group organized to overthrow a government or occupation force
Synonym(s): resistance
Hypernym(s): revolutionary_group
· 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'"
Synonym(s): metro, tube, subway_system, subway
Hypernym(s): railway, railroad, railroad_line, railway_line, railway_system
· under the level of the ground; "belowground storage areas"; "underground caverns"
Synonym(s): 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"
Synonym(s): clandestine, cloak-and-dagger, hole-and-corner, hugger-mugger, hush-hush, secret, surreptitious, undercover
· in or into hiding or secret operation; "the organization was driven underground"
· beneath the surface of the earth; "water flowing underground"