[1] : WordNet (r) 2.0

gangster
     n : a criminal who is a member of gang syn: mobster
see also:
mobster 

[2] : Moby Thesaurus II by Grady Ward, 1.0

59 moby thesaurus words for "gangster":
   judas, mafioso, bad person, bandit, betrayer, brigand, convict,
   criminal, crook, dacoit, deceiver, delinquent, desperado,
   desperate criminal, double-dealer, evildoer, felon, fugitive,
   gallows bird, gaolbird, goon, gunman, gunsel, gunslinger, hit man,
   hood, hoodlum, hooligan, jailbird, lawbreaker, malefactor,
   malevolent, malfeasant, malfeasor, misfeasor, mobsman, mobster,
   mugger, outlaw, public enemy, quisling, racketeer, robber, ruffian,
   scofflaw, sinner, skinhead, soldier, swindler, thief, thug,
   torpedo, tough, traitor, transgressor, two-timer, villain,
   worker of ill, wrongdoer

Gangster >> G Words
Gangster, definition of term: Gangster
gangster_pag1.html