How do you define a "social justice warrior"?

Someone who fights for the underdog.

I’ll explain how I view it rather than try to define it. They are believers in the social cause they fight for. They don’t simply take a position like most of us do, it’s more of a lifestyle and an identity for them. Normal people look at a situation and align themselves somewhere on the support spectrum. “Warriors” don’t, they always take the extreme position, adopt the “narrative” and will martyr themselves for it. It makes them feel special and in the process it can often narrow their mind to other perspectives. They often cease thinking rationally and will only take the side of the cause they are aligned with. They usually see people with other perspectives as “the enemy” and will become shockingly hateful toward them. “social justice warrior” is derogatory and it should be, it is not a compliment. There is another creature that earns this label but “social justice hipster” is more appropriate. You’ll find this pitiful beast shooting quick tweets or “like and repost” quick little rants they copied from someone else yet take credit for. If you are not identifying with them and are of a certain demographic they’ll recite the classic “check your privilege” ad hominem attack when attempting to debate with them. While some may actually be productive members of society many will be that smug waiter that can’t get your order right or that person on a bar stool with a can of PBR pontificating about society using big words that are unnecessary in a pathetic attempt to appear highly educated and intelligent. If they actually are highly educated they use said words to ego stroke themselves leaving little doubt that the cause they are ranting about is really about that and not the cause itself. Finally there is another, the “social justice opportunist” These people profit from social causes and in some cases actually stir the pot to make things worse for their own personal gain be it monetary or launching themselves into the limelight. They often take the role of “cult leader” feeding their flock of “true believers” piles of bullshit neatly garnished with bits of truth that give what they are saying an illusion of legitimacy. All that said there is nothing wrong with taking up a cause you believe in, that is healthy and should be encouraged but when people cross the sometimes blurry line into warriordom then this ceases to be the case.

It is a strawman term for right wingers to summarily dismiss the opposition without thought or effort.

This image sums up what I think about them

It’s a term made up by annoying people who have a broken-record complaint about people who annoyingly over-(ab)use the annoying expression “social justice”, which is an awful distraction from actual issues.