ism Syllabification: (ism)Pronunciation: /ˈizəm/Definition of ism noun informal, chiefly derogatory a distinctive practice, system, or philosophy, typically a political ideology or an artistic movement:of all the isms, fascism is the most repressiveDerivatives ist noun Origin: late 17th century: independent usage of -ismism in other Oxford dictionaries Definition of ism in the British & World English dictionary