Which term describes an acid that can donate more than one proton?

The term that describes an acid capable of donating more than one proton is "polyprotic acid." Polyprotic acids can release multiple protons, with the ability to donate two or more hydrogen ions (H⁺) in a stepwise manner. This characteristic is what distinguishes polyprotic acids from monoprotic acids, which can only donate one proton.

Some polyprotic acids may donate two protons (such as sulfuric acid, H₂SO₄), which would also be specifically described as diprotic acids, while those that can donate three protons (like phosphoric acid, H₃PO₄) are referred to as triprotic acids. Thus, while the terms "diprotic" and "triprotic" are more specific cases of polyprotic acids, the broader term captures all acids capable of donating more than one proton, making it the most appropriate answer.