cementite Syllabification: (ce·ment·ite)Pronunciation: /siˈmenˌtīt/Definition of cementite noun Metallurgy a hard, brittle iron carbide present in cast iron and most steels. Chemical formula: Fe3C Origin: late 19th century: from cement + -ite1cementite in other Oxford dictionaries Definition of cementite in the British & World English dictionary