gradual

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Occurring or developing slowly or by small increments.
• noun The liturgical book containing the chants for the Mass.
• noun A biblical text sung between the Epistle and the Gospel of the Mass.

from The Century Dictionary.

• Marked by or divided into degrees; proceeding by orderly stages or sequence; graduated.
• Moderate in degree of movement or change; proceeding with slow regularity; not abrupt or sudden: as, a gradual rise or fall of the thermometer; gradual improvement in health.
• noun A series of steps.
• noun In the Rom. Cath, Ch.: An antiphon sung after the reading of the epistle, while the book is moved from the epistle to the gospel side of the altar: so called because it was formerly sung by the subdeacon or epistler and cantor on the step (gradus) of the ambo or pulpit from which the epistle was read.
• noun An office-book formerly in use, containing the antiphons called graduals, as well as introits and other antiphons, etc., of the mass. Also called the cantatory or cantatorium.

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

• adjective Proceeding by steps or degrees; advancing, step by step, as in ascent or descent or from one state to another; regularly progressive; slow
• noun An antiphon or responsory after the epistle, in the Mass, which was sung on the steps, or while the deacon ascended the steps.
• noun A service book containing the musical portions of the Mass.
• noun obsolete A series of steps.

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

• 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.
• noun Roman Catholic Church An antiphon or responsory after the epistle, in the Mass, which was sung on the steps, or while the deacon ascended the steps.
• noun Roman Catholic Church A service book containing the musical portions of the Mass.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (Roman Catholic Church) an antiphon (usually from the Book of Psalms) immediately after the epistle at Mass
• adjective proceeding in small stages
• adjective (of a topographical gradient) not steep or abrupt