polyacid

from The Century Dictionary.

• In chem., of a base, equivalent in combining capacity to an acid radical of valence greater than unity.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry Any polybasic acid
• adjective chemistry polybasic