about-face

Short definition from Wiktionary

Noun

1. 1
   An abrupt turn to face the opposite direction.
2. 2
   A reversal in direction; a reversal of attitude or opinion.
3. 3
   Alternative spelling of about-face.

Verb

1. 1
   To turn 180 degrees to face the opposite direction.
2. 2
   To change opinion or attitude drastically.
3. 3
   Alternative spelling of about-face.