Trying to define the term Feminism is challenging because it means many different things to many different people.

My definition is quite simple.

Feminism is the movement for equal rights for women whatever that might entail during any given period in history.

Given my definition I don't accept the concept of "protofeminism" nor do I believe that there were only three "waves" of feminism.

That said, for now and in the interests of clarity, I will make my comments within the context of accepted historical standards.

Historically speaking there have been three "waves" of feminism defined.

The first wave began in the 18th century along with the development of the FreeThought movement and Rationalism and was supported by many FreeThinkers from it's inception.

It's neither an accident nor a coincidence that the suffragette leaders were FreeThinkers for the most part.

The reason for this is that it was the FreeThinkers who were questioning the standards and the existing beliefs, holding them up to the light of reason, discarding that which didn't meet rational standards and upholding that which did.

That's not to say that Christian women didn't play a role in fighting for the right to vote. They did. It was, in fact, the one unifying issue between Christian feminists and FreeThinking feminists.

However, there was a divergence of interest on other issues where the Christian feminists focused on Temperance (prohibition of alcohol) whereas the FreeThinking feminists focused on Abolition (banning slavery) amongst other issues.

While the stated focus of this First Wave was womens suffrage, the right to vote, it's real focus was much more than that.

It was about the right of women to recognized as persons under the law.

After all, that's precisely why women didn't have suffrage. We were legally considered chattel, the property of the men who were in charge of us whether they were our fathers, husbands, uncles, brothers, caretakers, etc.

Note that according to Amendment XIV of the US Constitution, citizens were persons and on those grounds granted the privileges defined by the Constitution including the right to vote. Since women were not given the right to vote they were not considered persons under the law or citizens as defined by the XIVth Amendment.

Amendment XIV

(The proposed amendment was sent to the states June 16, 1866, by the Thirty-ninth Congress. It was ratified July 9, 1868.)
Section 1

[Citizenship defined; privileges of citizens.]

All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.

Source: http://www.infoplease.com/ipa/A0749825.html

While the women of the day who posed arguments to support their right to equality did so within the context of the times and in relation to the existing social theories which kept them enslaved, the real issue was glaringly obvious and while unstated, was reflected clearly in Marion Kirkland Reid's, A Plea For Women (1843), where she elucidated three issues which stood in the way of women's rights. These three issues formed the foundation for both the First and Second Wave Feminist movements.

They were:
1. Lack of civil rights
2. Unjust laws against women
3. Inability to obtain an education

If women were considered human beings, people under the law, the above would have resulted in violations of the existing Constitutions in various western countries.

In addition, it was implicit in the existing social theories of the day which Reid also addressed:

1. women and domesticity
2. women and Christianity.

Reid spoke to these in the context of "women's appropriate role in society".

Source: http://www.pinn.net/~sunshine/whm2003/reid.html

So Reid's major contribution was to objectify through these issues the real problem which was that women were not considered to be persons under the law, by the society of the day.

Reid's document, combined with the shunning of women from around the world, who attended the first World Anti-Slavery Convention in 1840 led to the Seneca Falls Convention in the US, on women's rights. The Declaration of Rights and Sentiments was authored here by Elizabeth Cady Stanton, and became the foundation for American feminism.

Excerpt:
"We hold these truths to be self-evident: that all men and women are created equal; that they are endowed by their Creator with certain inalienable rights; that among these are life, liberty, and the pursuit of happiness; that to secure these rights governments are instituted, deriving their just powers from the consent of the governed. Whenever any form of government becomes destructive of these ends, it is the right of those who suffer from it to refuse allegiance to it, and to insist upon the institution of a new government, laying its foundation on such principles, and organizing its powers in such form, as to them shall seem most likely to effect their safety and happiness."

***

"Closing Remarks
Now, in view of this entire disfranchisement of one-half the people of this country, their social and religious degradation—in view of the unjust laws above mentioned, and because women do feel themselves aggrieved, oppressed, and fraudulently deprived of their most sacred rights, we insist that they have immediate admission to all the rights and privileges which belong to them as citizens of these United States."

Source: http://en.wikipedia.org/wiki/Declaration_of_Sentiments

Once suffrage, the right to vote, was won, a major hurdle was overcome. This right, through the XIXth Amendment of the US Constitution legally established that women were persons under the law.

Amendment XIX

(The proposed amendment was sent to the states June 4, 1919, by the Sixty-sixth Congress. It was ratified Aug. 18, 1920.)

[The right of citizens to vote shall not be denied because of sex.]

The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of sex.

[Congress given power to enforce this article.]

Congress shall have power to enforce this article by appropriate legislation.

Source: http://www.infoplease.com/ipa/A0749825.html

This allowed women to move things to the next level, to establish legal and social equality in other areas.

Women now began the process of establishing an identity through media and culture,  legal rights, employment inclusion and equity, reproductive rights, exploration of gender issues and female sexuality, fighting for social reform on many fronts including Family and Property Law.

None of these issues was won easily and at times resulted in the imprisonment of advocates.

In addition, many rights were removed after WWII since women were no longer needed in the work force.

This environment led to the Second Wave of Feminism.

Simone de Beauvoir, mother of modern feminism, existentialist philosopher, feminist, polyamorist, bisexual, lover of and inspiration to Jean Paul Sartre wrote the ground-breaking book, The Second Sex in 1949 which laid the foundation for this Second Wave of Feminism.

Beauvoir's critique of First Wave Feminism corrected errors in and advanced the philosophical approaches originally adopted by First Wave Feminism.

She established the concept that women's goal wasn't to be like men but to be equal to men, that equality was established by the freedom to choose, and was responsible for coining the term, Women's Liberation.

Source: http://en.wikipedia.org/wiki/History_of_feminism