stands for "Social Justice Warrior"
derogatory term for people who are basically overly in defense of whatever the popular beliefs portray as the greater victim of discrimination (usually SJWs would be defending women, african americans, homosexuals, etc).
A SJW against sexism might think that since women are so much moreso discriminated against than men, they should get special treatment.
They might also say that people who say that men are discriminated against should realize that since women are so much moreso discriminated against than men, that it's wrong/rude to defend men.
Social Justice Warrior. A pejorative term for an individual who repeatedly and vehemently engages in arguments on social justice on the Internet, often in a shallow or not well-thought-out way, for the purpose of raising their own personal reputation. A social justice warrior, or SJW, does not necessarily strongly believe all that they say, or even care about the groups they are fighting on behalf of. They typically repeat points from whoever is the most popular blogger or commenter of the moment, hoping that they will "get SJ points" and become popular in return. They are very sure to adopt stances that are "correct" in their social circle.
The SJW's favorite activity of all is to dogpile. Their favorite websites to frequent are Livejournal and Tumblr. They do not have relevant favorite real-world places, because SJWs are primarily civil rights activists only online.
A social justice warrior reads an essay about a form of internal misogyny where women and girls insult stereotypical feminine activities and characteristics in order to boost themselves over other women.
The SJW absorbs this and later complains in response to a Huffington Post article about a 10-year-old feminist's letter, because the 10-year-old called the color pink "prissy".
Commnter: "I don't like getting manicures. It's too prissy."
SJW: "Oh my god, how fucking dare you use that word, you disgusting sexist piece of shit!"
Social justice warrior, someone who fights for the principles of human equality and solidarity.
Jessica really educated me on the concept of white privilege after she got arrested for protesting the gentrification of Harlem. She's a real SJW.