SJW 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.