n. [ NL. sal aëratus; -- so called because it is a source of fixed air (carbon dioxide). See Sal, and and Aerated. ] (Old Chem.) Aerated salt; a white crystalline substance having an alkaline taste and reaction, consisting of sodium bicarbonate (see under Sodium.) It is largely used in cooking, with sour milk (lactic acid) or cream of tartar as a substitute for yeast. It is also an ingredient of most baking powders, and is used in the preparation of effervescing drinks. [ 1913 Webster ]