What's one of them, then?

Helen Mirren says "everyone should be a feminist" - but what exactly is a feminist? It's one of those words which can mean different things to different people.  At the one end of the spectrum, it is somebody who believes that men and women are equal and should be treated as such, whereas at the other end it is someone who believes that women are inherently superior to men and are only held back from their rightful place by a male-dominated society.  And of course all points between,  So I think Dame Helen needs to define what she understands by the word.