synthesizer Syllabification: (syn·the·siz·er)Pronunciation: /ˈsinTHəˌsīzər/Translate synthesizer | into French | into German | into Italian | into Spanish Definition of synthesizer noun an electronic musical instrument, typically operated by a keyboard, producing a wide variety of sounds by generating and combining signals of different frequencies. synthesizer in other Oxford dictionaries Definition of synthesizer in the British & World English dictionary