Source : Webster's Revised Unabridged Dictionary (1913)

Gradate \Gra"date\, v. t. [See {Grade}.]
   1. To grade or arrange (parts in a whole, colors in painting,
      etc.), so that they shall harmonize.

   2. (Chem.) To bring to a certain strength or grade of
      concentration; as, to gradate a saline solution.

Source : WordNet®

gradate
     v 1: arrange according to grades; "These lines are gradated"
     2: pass imperceptibly from one degree, shade, or tone into
        another; "The paint on these walls gradates but you don't
        see it"