triacetate Syllabification: (tri·ac·e·tate)Pronunciation: /trīˈasiˌtāt/ (also cellulose triacetate)Definition of triacetate noun a form of cellulose acetate containing three acetate groups per glucose monomer, used as a basis for man-made fibers. triacetate in other Oxford dictionaries Definition of triacetate in the British & World English dictionary