polyacid

having more than one replaceable hydrogen atom.

capable of reacting with more than one equivalent weight of an acid.

an acid having more than one replaceable hydrogen atom.

an oxyacid containing the equivalent of extra molecules of its anhydride, as the polysulfuric acids, H 2 S 2 O 7 or H 2 SO 4 ⋅SO 3 , and H 2 S 3 O 1 0 or H 2 SO 4 ⋅2SO 3 .