catalyst [catalysts](substance which increases the rate of a chemical reaction without being consumed in the process) noun [UK: ˈkæ.tə.lɪst] [US: ˈkæ.tə.ləst]
catalytic converter(a chamber which oxidises exhaust gases into carbon dioxide) noun [UK: ˌkæ.tə.ˈlɪ.tɪk kən.ˈvɜː.tə(r)] [US: ˌkæ.tə.ˈlɪ.tɪk kən.ˈvɝː.tər]