A lot of people level the charge that feminism is really hard to define and/or that everyone uses it differently. To an extent, that's fair. It really is hard to give clear content to any word that refers to a global movement (environmentalism can mean lots of things to lots of people in lots of places) or an amorphous concept (racism can refer to overt Jim Crow laws, subconscious suspicions (in the minds of perfectly progressive people) of those with different skin tones, or affirmative action, depending on context and who's speaking) that has been around for millennia. Feminism has this problem because it's a broad global issue and its causes have evolved and expanded a lot over time.
Those changes are particularly pertinent, I think. Often we think of feminist struggles historically as progressing from things like ending the legal status of married women being property to getting them the right to vote to allowing them to work in certain professions to removing cultural stereotypes that de facto prevent women, at least at the margins, from having all the choices men have. But not only do those direct changes on their own mean that feminism is a big thing, feminism has come to realize* that the "we" I spoke of above is referring largely to Western, white, middle and upper-class women. Largely separate issues exist for women outside this parochial bubble: women in (and emigrants from) the Middle East deal with issues like hijabs (which some insist are empowering and others see as oppressive) and honor killings and not being allowed to drive; women of color uniquely experience the intersection of race with gender, including discrimination within the feminist movement; some poor American women might as well live in a pre-Roe v. Wade world if they can't afford an abortion, etc.--not to even get into transphobia within feminist movements ("Men who chop off their penises are not women!!1 Ahhh, gross!"). All this is to say that feminism, whatever it is, is dealing with a lot of issues all at once. In some ways, it might not make a lot of sense to assign just one word to all of these disparate issues and causes and voices. And yet we do, and I think they all do have the common thread of women's treatment and opportunity running through them.
OK, so that is a bit about why I agree that it can be hard to pin down "feminism" for time and all eternity here or anywhere. But I think we can get a pretty decent definition that has some flexibility and covers the basics.
When I was thinking about this (Jeff kindly suggested I tackle the issue in the comments on my last post) I kind of came up with more of a description than a definition, but let's start there. I'd say that feminism is seeing problems with the way women are and have been treated in the world, coupled with a desire to change that injustice; it's believing that women are equal to men in intelligence, skill, thoughtfulness, kindness, and capacity for growth and change; it's wanting all people to have equal treatment from society and the law.
Now, I'm a big-tent person, whether we're talking about the Democratic Party, Mormonism, feminism, or what counts as art: I tend to err on the side of "sure, let 'em in!" So my definition of feminism allows for people who believe that men and women are significantly and inherently different, or for people who think that women and men complement each other such that sex with a member of the same sex is necessarily destructive. Of course, it also allows for people who think that essentialism is antithetical to feminism, or who think that anti-LGBT beliefs are incompatible with feminism, or who think that all bathrooms should be unisex! In other words, I'm ok with defining two people as feminist even if they think the other is harming the cause. Kinda like how I still think the Mormons who believe I'm hurting the church by being a liberal are still Mormons. Relatedly, I privilege self-identification over rigid rules. If someone wants to use the label feminist, I say the more, the merrier; on the contrary, I don't call people feminists even if they meet my definition if they don't want to use the label (even if in my head I would probably still classify them that way as a shorthand). Complicated, I know.
I also like Wikipedia's definition: "Feminism is a collection of movements and ideologies aimed at defining, establishing, and defending equal political, economic, and social rights for women. In addition, feminism seeks to establish equal opportunities for women in education and employment. A feminist is 'an advocate or supporter of the rights and equality of women.'" (NB: these are just summaries of dictionary definitions.) Equal rights, equal opportunities: yes! People who are on the side of women getting more power in the world (until they have equal power with men--let's not keep going so far we start harming men! [not that we're in much danger of that anytime soon...]) are feminists. In fact, even people who are glad that women have progressed as far as they have and just don't want to strip them of the right to vote are feminists in my book!
Feminism isn't that controversial or complicated to me at its basic level. We can get into all its waves and flavors and different people will be more or less attracted to the various aspects of those, but really I think most people agree that women have been mistreated for too long and are glad to see that changing, and thus are feminists--even you! (Yeah, I just called you a feminist--whatcha gonna do about it, tough gal?) That big-tent-ness can get dangerously close to covering everyone and thus no one, but think of it more as a spectrum. The more problems you see with the treatment of women historically and currently, and the more you're concerned about them, the more of a feminist you are.
What do you think? Is this a fair definition? Does it actually say anything or is it so much liberal sound and fury? Any major parts of feminism I should have included? Did I answer your question, Jeff? :)
* Here I gynomorphized (which is the counterpart to masculine anthropomorphizing) feminism by attributing consciousness to it.