alternate angles

plural noun Geometry.

1. two nonadjacent angles made by the crossing of two lines by a third line, both angles being either interior or exterior, and being on opposite sides of the third line.

pl n

1. two angles at opposite ends and on opposite sides of a transversal cutting two lines

1. 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.