Imagine you take a radius from the center of the shape, you add up all of the lines as it rotates 360 degrees. The radius is measured from its point of rotation, like (0,0) in Cartesian coordinates,to the point on the perimeter of a shape. Then you take the sum and divide by the intervals of rotation until the intervals become infinitesimal.
Is it called the radius of gyration, or is it a little bit different?