Meaning of circle of curvature

cir'cle of cur'vature

Pronunciation: [key]
— Math. Math.
  1. the circle with its center on the normal to the concave side of a curve at a given point on the curve and with its radius equal to the radius of curvature at the point. Also called
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.