incurvation

from WordNet (r) 3.0 (2006)

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

from The Collaborative International Dictionary of English v.0.48

Incurvation \In`cur*va"tion\, n. [L. incurvatio: cf. F.
   incurvation.]
   [1913 Webster]
   1. The act of bending, or curving.
      [1913 Webster]

   2. The state of being bent or curved; curvature.
      [1913 Webster]

            An incurvation of the rays.           --Derham.
      [1913 Webster]

   3. The act of bowing, or bending the body, in respect or
      reverence. "The incurvations of the knee." --Bp. Hall.
      [1913 Webster]