teratogen Syllabification: (te·rat·o·gen)Pronunciation: /teˈratəjən, -ˌjen, ˈterətəjən/Definition of teratogen noun an agent or factor that causes malformation of an embryo. Derivatives teratogenicPronunciation: /təˌratəˈjenik, ˌterətə-/ adjective teratogenicityPronunciation: /təˌratəjəˈnisitē, ˌterəˌtō-/ noun teratogen in other Oxford dictionaries Definition of teratogen in the British & World English dictionary