Source : Webster's Revised Unabridged Dictionary (1913)

Dilatation \Dil`a*ta"tion\, n. [OE. dilatacioun, F. dilatation,
   L. dilatatio, fr. dilatare. See {Dilate}, and cf. 2d
   {Dilation}.]
   1. Prolixity; diffuse discourse. [Obs.] ``What needeth
      greater dilatation?'' --Chaucer.

   2. The act of dilating; expansion; an enlarging on al? sides;
      the state of being dilated; dilation.

   3. (Anat.) A dilation or enlargement of a canal or other
      organ.

Source : WordNet®

dilatation
     n 1: the state of being stretched beyond normal dimensions [syn:
          {distension}, {distention}]
     2: the act of expanding an aperture; "the dilation of the pupil
        of the eye" [syn: {dilation}]