| 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. |
al·ter·nate angle (ôl'tər-nĭt, āl'-)  (click for larger image in new window) n. One of a pair of nonadjacent angles on opposite sides of a transversal that cuts two lines. The angles are both exterior or both interior to the two lines. |
| alternate angles
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. |