n.[theS]

1. （大寫）陰間，地獄
2. 下層社會；黑社會
   That quiet man was an underworld kingpin.

   那個安安靜靜的人是個黑社會老大哥。

   The pot trade is controlled by the underworld.

   毒品生意為黑社會所控制。

3. 【古】地球，大地

n.

1. the world of criminals or of organized crime.
2. the mythical abode of the dead, imagined as being under the earth.