Example: "In paris the subway system is called the `metro' and in london it is called the `tube' or the `underground'"
Example: "The organization was driven underground"
Example: "Water flowing underground"
Example: "Belowground storage areas"
Example: "Clandestine intelligence operations"
To route electricity distribution cables underground
Below the ground; below the surface of the earth.
Example: "There is an underground tunnel that takes you across the river."
Hidden, furtive, secretive.
Example: "These criminals operate through an underground network."
Outside the mainstream, especially unofficial and hidden from the authorities.
Example: "Underground music"