Source : Webster's Revised Unabridged Dictionary (1913)

Metaphosphoric \Met`a*phos*phor"ic\, a. [Pref. meta- +
   phosphoric.] (Chem.)
   Pertaining to, or designating, a monobasic acid, {HPO3},
   analogous to nitric acid, and, by heating phosphoric acid,
   obtained as a crystalline substance, commonly called glacial
   phosphoric acid.