Source : Webster's Revised Unabridged Dictionary (1913)

Polyacid \Pol`y*ac"id\, a. [Poly- + acid.] (Chem.)
   Capable of neutralizing, or of combining with, several
   molecules of a monobasic acid; having more than one hydrogen
   atom capable of being replaced by acid radicals; -- said of
   certain bases; as, calcium hydrate and glycerin are polyacid
   bases.