dioxide - an oxide containing two atoms of oxygen in the moleculecarbon dioxide, carbonic acid gas, CO2 - a heavy odorless colorless gas formed during respiration and by the decomposition of organic substances; absorbed from the air by plants in photosynthesis chlorine dioxide - an explosive gas (ClO2) used chiefly in bleaching paper or starch or soap or flour and in water purification oxide - any compound of oxygen with another element or a radical sulfur dioxide, sulphur dioxide - a colorless toxic gas (SO2) that occurs in the gases from volcanoes; used in many manufacturing processes and present in industrial emissions; causes acid rain |