Meaning of retrodirective

ret•ro•di•rec•tive

Pronunciation: (re"trō-di-rek'tiv, -dī-), [key]
— adj. Optics.
  1. (of a mirror, reflector, etc.) having three reflecting surfaces so oriented that a ray of light is reflected in a direction parallel but opposite to its original direction.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.