angle of reflection

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The angle formed by a reflected ray or wave and a line perpendicular to the surface at the point of reflection.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun optics The angle between the perpendicular and a ray reflected from a surface

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the angle between a reflected ray and a line perpendicular to the reflecting surface at the point of incidence