autotoxin Syllabification: (au·to·tox·in)Pronunciation: /ˈôtōˌtäksin/Definition of autotoxin noun a substance produced by an organism that is toxic to the organism itself. Derivatives autotoxicPronunciation: /ˌôtōˈtäksik/ adjective autotoxin in other Oxford dictionaries Definition of autotoxin in the British & World English dictionary