cacodylic acid Syllabification: (cac·o·dyl·ic ac·id)Pronunciation: /ˌkakəˈdilik/Definition of cacodylic acid noun Chemistry a toxic crystalline acid containing arsenic, used as a herbicide. Chemical formula: (CH3)2AsO(OH) Derivatives cacodylatePronunciation: /ˌkakəˈdilˌāt/ noun cacodylic acid in other Oxford dictionaries Definition of cacodylic acid in the British & World English dictionary