alternate angles definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
Geom. a pair of nonadjacent angles, one on each side of a transversal, that are both interior or both exterior: these paired angles are equal if the lines cut by the transversal are parallel
alternate angles - Science Definition
Two angles formed on opposite sides of a line that crosses two other lines. The angles are both exterior or both interior, but not adjacent.