volte-face

noun2

1. •
   A reversal of attitude, policy, or principle.

   • Psychoanalysis has sprung many surprises on us, performed more than one volte face before our indignant eyes. — 1921
2. •
   A dramatic change in mood or tone.

   • Shakespeare often used volte-faces in the rhyming couplets at the end of his sonnets.