Entry 1 sense Webster, 1913 Dioxide /dī-äk'-sīdˌ/ · Di·ox·ide · IPA /daɪˈɒksaɪd/ 01 n. An oxide containing two atoms of oxygen in each molecule; binoxide. 1. An oxide containing two atoms of oxygen in each molecule; binoxide.(Chem.) [Obs.] Phrases & compounds Carbon dioxide — See Carbonic acid, under Carbonic.