Source : Webster's Revised Unabridged Dictionary (1913)

Gradation \Gra*da"tion\, n., [L. gradatio: cf. F. gradation. See
   {Grade}.]
   1. The act of progressing by regular steps or orderly
      arrangement; the state of being graded or arranged in
      ranks; as, the gradation of castes.

   2. The act or process of bringing to a certain grade.

   3. Any degree or relative position in an order or series.

            The several gradations of the intelligent universe.
                                                  --I. Taylor.

   4. (Fine Arts) A gradual passing from one tint to another or
      from a darker to a lighter shade, as in painting or
      drawing.

   6. (Mus.) A diatonic ascending or descending succession of
      chords.

Gradation \Gra*da"tion\, v. t.
   To form with gradations. [R.]

Source : WordNet®

gradation
     n 1: relative position in a graded series; "always a step
          behind"; "subtle gradations in color"; "keep in step
          with the fashions" [syn: {step}]
     2: a degree of ablaut [syn: {grade}]
     3: the act of arranging in grades [syn: {graduation}]