boric acid

Short definition from Wiktionary

Noun

1. 1
   H₃BO₃; B(OH)₃; a white crystalline solid, soluble in hot water to form a weak acid. Used as a mild antiseptic, flame retardant, insecticide, and in the manufacture of borax and other borate salts.
2. 2
   A hydrate of boric oxide, specifically any of the three acids orthoboric acid, metaboric acid, or pyroboric acid.