Dictionary.net

• the radius of the circle of curvature; the absolute value of the reciprocal of the curvature of a curve at a given point

2006 - WordNet 3.0
By Princeton University

• the radius of the circle of curvature; the absolute value of the reciprocal of the curvature of a curve at a given point

2011 - English Dictionary Database
By DataStellar Co., Ltd