polar subnormal

polar subnormal

[′pō·lər səb′nȯr·məl]
(mathematics)
For a given point on a plane curve, the projection of the polar normal on the radial line of the polar coordinate system that is perpendicular to the radial line to the given point.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.