Source : Webster's Revised Unabridged Dictionary (1913)

Incurvation \In`cur*va"tion\, n. [L. incurvatio: cf. F.
   incurvation.]
   1. The act of bending, or curving.

   2. The state of being bent or curved; curvature.

            An incurvation of the rays.           --Derham.

   3. The act of bowing, or bending the body, in respect or
      reverence. ``The incurvations of the knee.'' --Bp. Hall.

Source : WordNet®

incurvation
     n 1: a shape that curves or bends inward [syn: {concave shape}, {concavity},
           {incurvature}]
     2: the action of creating a curved shape