By definition, a person who believes in the fundamental equality between the sexes, with a focus upon women's issues such as equal pay or stereotyping.
However, those who call themselves feminists rarely abide by the dictionary term. A more appropriate term for the feminist of today is female chauvinist, one who believes the female sex is naturally superior to the male sex.
Those that call themselves feminist typically subscribe to second-wave feminism, which evolved in the 1970s from the earlier, first-wave feminism. Whereas first-wave feminism sought legislation that would grant equal protection under the law, second-wave feminism sought an overthrow of what they called "patriarchy," which included traditional families and capitalism.
Contrary to many feminist claims, feminism is not a belief that is exclusive to women. Some feminists object to men referring to themselves as feminist, and use the term "pro-feminist" instead. A man who believes in equal protection under the law can be classified as feminist by definition.
Feminists and feminist organizations tend to campaign for issues they percieve as important to women, such as abortion rights (most feminists are pro-choice), domestic violence, LGBT rights, and similar issues. Feminism is often criticized for a unilateral approach to their issues, focusing only on increasing the rights of women, even to the point of denying the rights of men, underscoring the importance of those issues in relation to men (such as Dr. Laura stating that men had more to fear from violence then women, as they were attacked more often, and being subsequently villified by feminists.)
Feminism has garnered much criticism for it's methods and statistics, and has been accused of violating it's own edicts. Among parents, mothers are more likely to murder their children then their fathers according to the FBI, yet feminist organizations push that single-parenthood, with maternal custody, is in the best interests of the child. Alternatively, feminist organizations equate any time a rape or domestic violence (female) victim is required to present evidence to prove her claims as "blaming the victim." Feminist organizations want to apply the precautionary principle, accepting the allegation at face value to "protect the victim." Critics counter by stating victims can provide evidence to the courts, and that precautionary principles without checks and balances allow women to exploit the legal system for profit.
Backlash further against feminism can also be found in statements that are misandrist, or hatred of males. Valerie Solonas is one of the most popular, having written a book about killing men. Mary Daly, a theologian who was fired for refusing to admit a male student who was otherwise qualified for her class, also advocated creating a "male-free" paradise. Other misandrists include Robin Morgan, Andrea Dworkin, Gloria Allred, and Catherine MacKinnon.
The family down the street believes in feminism. They believe special treatment that favors men or women is inherently sexist.
Major feminist organizations are not feminists. They believe in gaining special treatments for women and depriving those rights of men. To justify this, they usually use vague statments such as "ignorance of male privlege."