criminal, concerned with organized crime, Mafialike, gangster, mob-ruled; see also illegal, wicked 1.
Hades, Inferno, netherworld, otherworld; see hell 1.
gangland, gangdom, rackets, organized crime, the mob, the Syndicate, the Mafia, the Cosa Nostra, the Black Hand, criminals, riffraff.
"underworld." YourDictionary, n.d. Web. 09 June 2018. <http://thesaurus.yourdictionary.com/underworld>.
underworld. (n.d.). Retrieved June 09th, 2018, from http://thesaurus.yourdictionary.com/underworld