1. Also called orthoboric acid . Chem., Pharm. a white, crystalline acid, H 3 BO 3 , occurring in nature or prepared from borax: used chiefly in the manufacture of ceramics, cements, glass, and enamels, for fireproofing, and in medicine in aqueous solution as a mild antiseptic.
2. Chem. any of a group of acids containing boron.
[ 1865-70 ]