There is no "actual" (i.e., universally accepted) definition of feminist, any more than there is of "Christian." My favorite, and the one that I use, is: any person who recognizes that women have been and are frequently oppressed, and believes that something should be done about it.

My next realization was that I'm not really interested in associating with anyone who's not a feminist by this definition, which makes me slightly uneasy because I try to be accepting of others...and yet...

Oh, and there's also one of my personal beliefs expressed as buttons pinned on my backpack, which is: "Feminism is the radical notion that women are people," which I think does sum it up nicely.