noun
: a compound SO 2 that is toxic especially to plants, that occurs in the gases from volcanoes, in many volcanic springs, and in variable amounts in the atmosphere, that is produced as a heavy colorless nonflammable gas of pungent suffocating odor usually by burning sulfur or sulfides (as pyrite) and is present in the waste gases from many smelting and other industrial processes, that is easily condensed to a colorless liquid boiling at -10° C and is usually sold in liquid form, and that is used chiefly in making sulfuric acid, sulfites, other sulfur compounds, and sulfite pulp, and in petroleum refining as a reducing and bleaching agent, as a preservative, disinfectant, and fumigant, and as a refrigerant — see sulfurous acid