According to the Urban Dictionary, Social Justice Warrior is 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.” Then, in order to feel even more important, they bully others who disagree with their phony opinions.
In other words, SJW’s are phonies, adopting phony justice “positions” to feel good about themselves and to be “popular”, while trying to make other people feel bad about themselves. In reality, they have accomplished nothing and have nothing to feel good about.