I'd like to take this moment to point out that all forms of binarism are bad. (Including the binarist notion that all things are either "good" or "bad".) I feel like this has to be pointed out because we, every one of us, has a nasty habit: in our overzealousness to tear down one binary, we do so by reinforcing other binaries. So let me say again. All forms of binarism are bad.
It's well-known that I've had a long, fraught history with certain "feminist" communities, due to which I have heretofore disavowed that label. Because of these persistent conflicts, around ten years ago I retreated from feminist circles and communities. However, over the past year I have rejoined a number of feminist circles— or rather, I have joined womanist, black feminist, transfeminist, and queer feminist circles. And thanks to this reinvolvement with feminist activism I have come, once again, to feel a certain attachment to that word: "feminist". The attachment feels strange to me now, having disavowed it for so long in favor of "womanism", "black feminism", "transfeminism", and "queer feminism". But because of this attachment I feel, once more, the need to reclaim feminism away from those "feminist" communities whose philosophy and political methods I continue to disavow.
Hereafter, feminism is defined to be the philosophy that all forms of binarism are bad and that all forms of systemic binarist oppression must be dismantled before we can achieve justice and equality. While other movements may share this philosophy, feminism is distinguished (if that's even necessary) by focusing on the ways that sexual/gender-based binaries interact with, compound, reinforce, and are reinforced by other binaries.
I emphasize the plurality: binaries. Historically, communities using the "feminist" label have been misguided by restricting themselves to combating a single binary. Such a restriction is fundamentally at odds with feminism. Binaries interact to compound and reinforce one another, and therefore it is impossible to dismantle any singular binarism without also addressing the numerous other binarisms that particular binary interacts with. I have always believed this, but I am in no way unique in this belief. An important facet of this interaction between binaries is addressed by intersectionality, a term which originated in womanist and black feminist literature, but which has recently been co-opted, misunderstood, and watered down by mainstream white feminist communities. This belief is also reflected in the fracturing of "third wave" feminism in the 1990s as women of color, poor women, trans women, non-US women, sex-positive women, bisexual women, and numerous other communities became increasingly disillusioned with mainstream educated white middle-class american able-bodied unisexual cisgender feminism. For brevity, I will refer to this latter narrow-focused movement as "pseudofeminism".
Sexism refers to any of the many forms of systemic oppression arising from sexual/gender-based binaries. This includes but is not limited to traditional sexism, oppositional sexism, cissexism/transphobia, heterosexism/homophobia, unisexism/biphobia, monosexism/polyphobia, masculine-centrism/femmephobia, male-centrism/misogyny, transmisogyny, misogynoir, transmisogynoir, and so on.
Traditional sexism, misogyny, and male-centrism are the forms of sexism that have been the traditional focus of pseudofeminism. These forms of sexism arise from male/female binarism and the systemic overvaluation of men and undervaluation of women. Notably, male/female binarism should be distinguished from masculine/feminine binarism and the systemic overvaluation of masculine identities and activities and undervaluation of feminine identities and activities, from which masculine-centrism, femmephobia, and misogyny arise. Although pseudofeminism fights against the marginalization of women, it does so in a way that reinforces the marginalization of feminine people. While pseudofeminism asserts that women can do anything men can do, it claims that this is only possible through the masculinization of women. Feminine women are still devalued and looked upon as traitors to the cause. Femininity has no place in pseudofeminism, a fact which has driven many women away from feminism proper. The importance of distinguishing male/female binarism from masculine/feminine binarism, and the ramifications of a feminism which does not marginalize femininity, are one of the main topics of Julia Serano's Whipping Girl.
Oppositional sexism, cissexism, and transphobia are the other main topic of Whipping Girl. Oppositional sexism also arises from male/female binarism, though in a different way than traditional sexism. Traditional sexism is the belief that men are better than women; whereas, oppositional sexism is the belief that men and women are "opposite" genders. If men and women are in opposition, then for men to be strong we must have that women are weak, for men to be logical women must be irrational, and so on. This oppositional ideology serves to reinforce traditional sexism: since being strong, rational, etc is is considered better than being weak, irrational, etc, and since men are supposedly the former whereas women are supposedly the latter, therefore men are "better" than women. Moreover, if men and women are opposites then the existence of trans people is unconscionable. If men and women are so diametrically opposed then how can one interpret a "man" who "becomes" a woman, or a "woman" who "becomes" a man? Still further, oppositional sexism additionally marginalizes all people with non-binary genders or with non-traditional binary genders. Thus, the oppositional structure of male/female binarism serves to marginalize not only women, but also trans people, genderqueer people, and other gender-minorities. Consequently, to dismantle traditional sexism against women it is necessary to also dismantle oppositional sexism and male/female binarism, from which it is self-evident that feminism must address not only the issues faced by cis women but also the issues faced by trans women and even by those who do not identify as women at all.
This oppositional structure applies not only to male/female binarism, it also applies to masculine/feminine binarism. This can be seen by the "opposition" between butch and femme identities, and the subsequent marginalization of those who do not fit into either category. This butch/femme oppositionalism is seen not only in lesbian communities but also in gay communities and often in queer communities more generally. It is also seen in in straight communities in the marginalization and invisiblization of non-stereotypically masculine men and non-stereotypically feminine women. Terms like "tomboy" are often used to marginalize non-stereotypically feminine women, to single them out as different from, and less desirable than, "normal" women. And we have an ideological narrative that tomboys will eventually find the right boy, she'll decide to become feminine in order to win him, and they'll live happily ever after. This conversion narrative serves to invisiblize tomboys by declaring that it's "just a phase" and that she'll "grow out of it". We have similar ideological narratives which construct feminine women as being somehow incapable of being intelligent ("dumb blonde"), mathematical/scientific ("geek girl"), playful ("gamer girl"), or possessing any number of other highly valued properties. Many of these terms ("tomboy", "geek girl", "gamer girl") are in the process of being reclaimed, but doing so requires overthrowing these sexist narratives which marginalize and invisiblize those who do not fit into masculine/feminine oppositionalism.
In addition to male/female binarism, another source of cissexism and transphobia is cis/trans binarism. The systemic valuation of cis identities over trans identities should need no explanation. (Though the invisiblization of trans people by the cisgender assumption deserves note.) The oppositional structure of cis/trans binarism serves, once again, to marginalize and invisiblize other forms of gender non-conformity. The marginalization of crossdressers is discussed at great length in Whipping Girl, as it features prominently in the medicalization and artificialization of trans women. In addition, cis/trans oppositionalism also serves to erase genderqueer, gender-fluid, and similar identities (which I shall group together under the acronym GQ). All too often the erasure of GQ identities is performed by trans people as they seek to legitimize transgenderism as a real phenomenon and to point out cissexism. Consequently, the larger gender non-conforming community tends to split along TG vs GQ lines, and this splitting undermines the ability of TG/GQ communities to protect themselves legally, medically, and socially. Moreover, the splitting off of TG/GQ communities from pseudofeminist communities in the 1990s weakens both communities and undermines both their causes. Political coalitions are necessary for minorities to overcome systemic oppression, which is why we must move away from fractive pseudofeminist ideology and embrace feminism.
Another binarist assumption is hetero/homo binarism. The systematic marginalization of homosexual identities and activities, again, needs no explanation; but, again, the oppositionalism is too often overlooked. The assumption that every person is either heterosexual or homosexual erases everyone who does not fall neatly into those categories, including not only bisexuals but also asexuals. In chapter 9 of Julia Serano's Excluded she discusses ways in which hetero/homo oppositionalism erases bisexual identities. It is not enough to recognize that homosexuality is devalued in our society, we must also recognize the role that invisibilizing bisexuality plays both in marginalizing bisexuals themselves and also in setting up homosexuals as being so different from heterosexuals that the two can never be reconciled. That is, the erasure of bisexualities is a tactic used to support the marginalization of lesbians and gays. While there is a great deal of literature on bi-invisibility, the closely related issue of ace-invisibility (the systemic invisiblization of asexuals and asexuality) is, to my knowledge, very little studied. However, it is telling that asexuals and aromantics tend to attach themselves to transgender and genderqueer communities rather than to lesbian and gay communities. (That there are practically no bisexual communities is also addressed in chapter 9 of Excluded.)
There will be opposition to including the fight against hetero/homo binarism under the banner of feminism. However, despite that resistance, feminism has already been fighting this battle for some time. The "lesbian-feminist" movement of the 1970s put forth the ideology that any "true" feminist must be a lesbian, since sleeping with men is consorting with the enemy. While lesbian-(pseudo)feminism has been passé for some time now, it has served to unite the fight against the marginalization of lesbians with the fight against the marginalization of women, and very few lesbians would consider themselves non-feminists. But if we are to eliminate the heterosexism faced by lesbians, along the way we must also eliminate the heterosexism faced by gays, bisexuals, and asexuals— for it is heterosexism itself we seek to eliminate.
I put forth that feminism must also combat monosexism (the sexism enacted against polyamory and polyamorists). The monosexual assumption invisiblizes polyamorists in much the same way that the unisexual assumption invisiblizes bisexuals, the sexual assumption invisiblizes asexuals, the heterosexual assumption invisiblizes homosexuals, the masculine assumption invisiblizes femmes, and the male assumption invisiblizes women. Moreover, there is a natural alliance between feminists and at least some polyamorists. Forms of polyamory are common in queer communities, so addressing the lives of queer people must already include addressing consensual non-monogamy. In addition, polygamy is decried by both feminists and polyamorists and for much the same reasons. Feminists and pseudofeminists have typically focused on the disempowerment and subjugation of the wives, whereas polyamorists typically focus on the non-consensual nature of the marriage; but both arguments resonate with both communities. The importance of consent is a fundamental assumption of feminism, and equality among partners is a crucial component of polyamory.
While white/color binarism is not the central focus of feminism, it cannot be overlooked. As pointed out by womanists and black feminists, women of color do not simply face both racism and sexism. The degree of oppression WOC face from racism and sexism is not additive, it's multiplicative. Moreover, racism against WOC is sexualized and sexism against WOC is racialized. Both of these factors —the multiplicative nature of belonging to multiple minorities, and the "flavoring" of oppressive acts— arise from the intersectionality of multiple forms of marginalization. Notably, intersectionality does not merely mean that some people belong to multiple marginalized groups and that we must listen to these people (though they do, and we must). And intersectionality does not merely mean that oppressions are multiplicative rather than additive (though they are). The hybridization and flavoring of oppression is crucial to understanding the challenges faced by those who live in the intersections. The racist actions men of color endure are distinct and different from the racist actions women of color endure; to combat racism we must recognize that difference. And the effects of sexism on men of color are different and distinct from the effects of sexism on women of color, and we must recognize that if we are to combat the effects of sexism. The term "misogynoir" was coined to capture the intersectional sexual/racial oppression faced by women of color, especially black women. Similarly, "transmisogyny" refers to the intersectional cissexist/misogynistic oppression faced by trans women; and "transmisogynoir" refers to the intersectional racist/sexist/cissexist oppression faced by trans women of color. If the misogyny against cisgender white women is to be eliminated, along the way we must also eliminate misogynoir, transmisogyny, and transmisogynoir, and to do so we must recognize not only the similarities between these various forms of oppression but also their differences.
Sexism is insidious. When you push too hard on one binarism the bigotry, hatred, and fear attached to it will simply reattach itself to some other binarism. This is made clear by the forms that sexism takes today. We no longer endure the overt traditional sexism of the past, instead we face subtle deniable forms of sexism. The well-actuallys and not-all-mens and well-I-just-likes and derailing and mansplaining and everything else serve to keep women "in their place" just as well as the discriminatory hiring practices and devaluation of women's labor and sexual violence and all that did in the 1950s (and still does).
This is my feminism. In order to destroy any form of gender- or sexual-oppression we must recognize and address every form of sexual/gender-oppression, and to do this means we must take seriously the intersectionalities faced by all sexual/gender minorities— including but in no way limited to women of color, trans women, queer women, bi women, poly women, poor women, disabled women, sex workers, non-US citizens, inter alia.
 In some literature "monosexism" is used to refer to what I call "unisexism" (the systemic marginalization of people who are not exclusively attracted to one sex/gender). I prefer to align mono/poly together and uni/bi together for etymological reasons.
 I phrase this as white/color binarism to focus on the ways that certain ethnicities are erased by the distinction between "White" people and "people of color". For example, many american indian people are read either as White as asian, but seldom as indian, and must learn to navigate this racist landscape; similarly to how bisexuals are read as either het or lesbian/gay, but never as bi. White/color binarism also serves to erase many black americans who are typically read as White. However, this is far from being the only racist binary. Another is white/black binarism, which serves to marginalize black people in specific ways that other people of color do not face, and which serves to invisiblize the wide range of ethnicities which are neither White nor black.
 Living in a cis-het-male supremacist culture affects everyone; just as living in a white supremacist culture affects everyone. The racism black men experience is often sexualized, due to the long history of grouping black men together with white women in opposition to white men (erasing black women along the way). Moreover, having been inundated with sexist messages and having one's expressions of gender heavily policed, black men (like everyone else) often internalize that sexism.
Edit 2014.07.13: Added footnotes  and .