Pyroboric

Pyr`o`bo´ric


a.1.(Chem.) Pertaining to derived from, or designating, an acid, H2B4O7 (called also tetraboric acid), which is the acid ingredient of ordinary borax, and is obtained by heating boric acid.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.