The American military drill command about-face, dating from the late 19th century, originally meant to turn about in the opposite direction. That meaning remains, but about-face is now more commonly used figuratively to mean a complete, sudden change in position, principle, or attitude. As a verb, it means to change one’s mind completely.
In all its uses, about-face is hyphenated.
In these sentences, about-face is a noun:
The publisher of the UK’s Yellow Pages directories is implementing a strategic about-face to reduce its reliance on shrinking print revenues. [Financial Times]
In an about-face, the Veterans Affairs Department announced today that several thousand more caregivers of severely disabled Iraq and Afghanistan vets will receive monthly stipends. [USA Today]
Early bans in New York City and other places may have sped up the food industry’s about-face on trans fats. [Chicago Sun-Times]
And the following are examples of the rarer verb sense of about-face:
But sensing doom, they about-face and return to the house. [Boston Globe]
Oakenfold remembers the skepticism coming from, in particular, Euro music magazines, which have about-faced and are now onboard. [Las Vegas Review-Journal]