“Social Justice Warrior”, commonly abbreviated as “SJW”, is a pejorative term for a person expressing or promoting socially progressive views, particularly relating to social liberalism, political correctness or feminism. The accusation of being an SJW implies that a person is engaging in disingenuous social justice arguments or activism to raise his or her personal reputation. In internet and video game culture the phrase is broadly associated with the Gamergate controversy and wider culture war fallout, including the 2015 Sad Puppies campaign that affected the Hugo Awards.

Origin and Meaning
In August 2015, the derogatory term “Social Justice Warrior” was one of several new words and phrases added to Oxford Dictionaries. Discussing the new addition, Abby Ohlheiser wrote in The Washington Post that “social-justice warrior” or variations thereof had been used as a laudatory phrase in the past, and provided an example dating to 1991. She quoted Katherine Martin, the head of U.S. dictionaries at Oxford University Press, who said, “All of the examples I’ve seen until quite recently are lionizing the person”. Ohlheiser wrote that the derogatory phrase had “emerged as the preferred term among the Gamergate movement for the people they believed to be their greatest enemies.” In discussing the term’s origin, Martin outlined the similarity with the pejorative use of “political correctness” to denigrate something, stating that “the perceived orthodoxy [of progressive politics] has prompted a backlash among people who feel their speech is being policed.”

https://en.wikipedia.org/wiki/Social_Justice_Warrior