polyacid

[ pol-ee-as-id ]
/ ˌpɒl iˈæs ɪd /
Chemistry

adjective

having more than one replaceable hydrogen atom.
capable of reacting with more than one equivalent weight of an acid.

noun

an acid having more than one replaceable hydrogen atom.
an oxyacid containing the equivalent of extra molecules of its anhydride, as the polysulfuric acids, H2S2O7 or H2SO4⋅SO3, and H2S3O10 or H2SO4⋅2SO3.

Origin of polyacid

First recorded in 1855–60; poly- + acid