Feminism is a sphere, not a continium, of beliefs, the core of which is that women are oppressed, one way or another, and something must be done about. You have various shades of lesbian sepratists like Janice Raymond and Mary Daly, fundamentalist feminists like Andrea Dworkin and Catherine MacKinnon, pro-sex feminists like Pat Califia and Jill Nagle, your various NOW types, people who combine feminism with other concepts of oppression, like bell hooks, and everything in between and overlapping, and pretty much whatever else you can think of. Critics of feminism all to often percieve feminism as one thing, or as simply a collection of 'reasonable' fminists and radical militant loonies who call for the destruction of all men.

Far be it from me, as a man, (or anyone else for that matter, I guess,) to define feminism once and for all, but this is the definition I use, and it seems to work the best.