about-face

noun

1. Military. a turn of 180° from the position of attention.
2. a complete, sudden change in position, direction, principle, attitude, etc.: They’ve done an about-face in their foreign policy.

verb (used without object), a·bout-faced, a·bout-fac·ing.

3. to execute an about face.
4. to turn in the opposite direction.
5. to switch to an opposite opinion.

interjection

1. (used as a military command to perform an about-face).