Added 10 October 2026 trioxide /trʌɪˈɒksʌɪd/ noun Categories: NatureRare Words noun ! Definition from WordNet 3.1, Princeton University. Pronunciation from Wiktionary, via Kaikki.org. More about trioxide at Wordnik → Where our words come from → An oxide containing three atoms of oxygen in the molecule. Related Words: dioxidepentachloridesulfuricarsenicanhydridesulphuricantimonytrioxidtritoxidetrioxygentrioxotetroxide Back to today's word