underground

Meanings

1. 1
   adv

   beneath the surface of the earth

   water flowing underground

2. 2
   adv

   in or into hiding or secret operation

   the organization was driven underground

3. 3
   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'

4. 4
   adj

   Below the ground; below the surface of the Earth.

   There is an underground tunnel that takes you across the river.

5. 5
   adj

   Hidden, furtive, secretive.

   These criminals operate through an underground network.

6. 6
   adj

   Of or relating to an art forms (such as music) or subculture that is outside the mainstream, especially one that is unofficial and hidden from the authorities.

   underground music

7. 7
   adv

   Below the ground.

   The tunnel goes underground at this point.

8. 8
   noun

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

   London Underground

Etymology

From Middle English undergrounde (adverb), equivalent to under + ground or under- + ground. Compare Dutch ondergrond, ondergronds, German Untergrund, Danish undergrunds.