1. The criminal class
   "The underworld controlled much of the city's illegal activities"
    
2. (religion) the underworld or abode of the dead in Hebrew theology
   "Ancient myths often described heroes descending into the underworld";
   - Hell, Hades, infernal region, netherworld, Sheol

Derived forms: underworlds

Type of: class, fictitious place, imaginary place, mythical place, social class, socio-economic class, stratum

Encyclopedia: Underworld