curvature of the spine

Curvature \Cur"va*ture\ (k?r"v?-t?r; 135), n. [L. curvatura. See
   {Curvate}.]
   1. The act of curving, or the state of being bent or curved;
      a curving or bending, normal or abnormal, as of a line or
      surface from a rectilinear direction; a bend; a curve.
      --Cowper.
      [1913 Webster]

            The elegant curvature of their fronds. --Darwin.
      [1913 Webster]

   2. (Math.) The amount of degree of bending of a mathematical
      curve, or the tendency at any point to depart from a
      tangent drawn to the curve at that point.
      [1913 Webster]

   {Aberrancy of curvature} (Geom.), the deviation of a curve
      from a circular form.

   {Absolute curvature}. See under {Absolute}.

   {Angle of curvature} (Geom.), one that expresses the amount
      of curvature of a curve.

   {Chord of curvature}. See under {Chord}.

   {Circle of curvature}. See {Osculating circle of a curve},
      under {Circle}.

   {Curvature of the spine} (Med.), an abnormal curving of the
      spine, especially in a lateral direction.

   {Radius of curvature}, the radius of the circle of curvature,
      or osculatory circle, at any point of a curve.
      [1913 Webster]