An abrupt turn to face the opposite direction.

“The soldier did an about-face and marched off.”

A reversal in direction; reversal of attitude or opinion.

“When Luke heard the news, he did an abrupt about-face on the policy.”

To turn 180 degrees to face the opposite direction

“The soldiers would about-face immediately after the order was given.”

To change opinion or attitude drastically.

“A politician will about-face at the drop of a hat if he thinks there are votes in it.”