a white, crystalline compound, HBO, with the properties of a weak acid, used as a mild antiseptic and in the manufacture of glass, enamels, flame retardants, etc.
See boric acid in American Heritage Dictionary 4
noun
A water-soluble white or colorless crystalline compound, H3BO3, used as an antiseptic and preservative and in fireproofing compounds, cosmetics, cements, and enamels.