polyethylene terephthalate Syllabification: (pol·y·eth·yl·ene ter·eph·thal·ate)Pronunciation: /ˌterə(f)ˈTHalˌāt/ (abbreviation: PET)Definition of polyethylene terephthalate noun a synthetic resin made by copolymerizing ethylene glycol and terephthalic acid, widely used to make polyester fibers. polyethylene terephthalate in other Oxford dictionaries Definition of polyethylene terephthalate in the British & World English dictionary