cacodylic acidEnglishOxford Dictionary of Englishcacodylic acid /ˌkakə(ʊ)dʌɪlɪk ˈasɪd , ˌkakə(ʊ)dɪlɪk ˈasɪd / ▸ noun [mass noun] Chemistry a toxic crystalline acid containing arsenic, used as a herbicide. Chemical formula: (CH3)2AsO(OH).