When one completely reverse one's point of view on an issue. For example, "After, John Howard saw the polls on reconciliation with the Aboriginal community; he made an about face and apologised for Australia's past injustices, after years of refusing to do so". Now if only this were to come true ...
About Face is also the name of one of David Gilmour's solo albums (he's the guitarist from Pink Floyd. It's not great stuff. While his guitar-playing is up-to-scratch, the songwriting sucks. Well, not sucks, it's just mediocre.