1. adjective
Proceeding by steps or small degrees; advancing step by step, as in ascent or descent or from one state to another; regularly progressive; slow; as, a gradual increase of knowledge; a gradual decline.
2. noun
a) An antiphon or responsory after the epistle, in the Mass, which was sung on the steps, or while the deacon ascended the steps.
b) A service book containing the musical portions of the Mass.
Wikipedia foundation.