1. (noun)Mafia, Maffia, Cosa Nostra a crime syndicate in the United States; organized in families; believed to have important relations to the Sicilian Mafia
2. (noun)Mafia, Maffia, Sicilian Mafia a secret terrorist group in Sicily; originally opposed tyranny but evolved into a criminal organization in the middle of the 19th century
3. (noun)mafia, maffia any tightly knit group of trusted associates