What is the meaning of Underground?

Below the ground; below the surface of the Earth.

Hidden, furtive, secretive.

Outside the mainstream, especially unofficial and hidden from the authorities.

Below the ground.

Secretly.

Regions beneath the surface of the earth, both natural (eg. caves) and man-made (eg. mines).

Synonym of subway: a railway that is under the ground.

A movement or organisation of people who resist political convention.

A movement or organisation of people who resist artistic convention.

To route electricity distribution cables underground.

underground (culture)

underground (outside the mainstream)

the underground (people who resist artistic convention)

the underground (people who resist artistic convention)

underground

underground (movement)

Source: wiktionary.org