- any of the four angles formed on the outside of two straight lines when crossed by a transversal
- an angle formed by any side of a polygon and the extension of the adjacent side
- The angle between any side of a polygon and an extended adjacent side.
- Any of the four angles that do not include a region of the space between two lines intersected by a transversal.
Angles 1, 2, 7, and 8 are exterior angles.