Social Justice Warrior (SJW) is not a descriptive term with any usefulness, but a vague insult that only ever helps push right-wing ideologies.
At best, 'SJW' is used to group together individuals with unrelated viewpoints that just happen to be considered progressive. Different types of feminists, Black Lives Matter activists, queer theorists, and so on, are all declared members of 'SJW movements', and therefore the worst behavior and most extreme beliefs held by individuals from any of these groups can be used as examples in the fight against any one of these groups. It serves as a way for to dismiss people's opinions automatically based on things these people never actually said, heard, or ever agreed with. For example, one person says (probably flippantly) that all men should be killed, and and another person says that they are a feminist because they believe in equality of the sexes. If you ask for an example of a Social Justice Warrior, you will be shown the first person, but as a label it will still be extended to the second and then used to cut them out of discussion. Many cowardly neoliberal types shy away from identifying with causes that their views actually align with completely just because they have fallen victim to the 'anti-SJW' propaganda game.
More commonly, and even worse, a SJW is anyone to the left of Trump's Republican Party. The Democrats are said to be a party of Social Justice, and any minor disagreement with conservative figures is a sign that they have been infected with SJW ideology. There is a very little nuance, and a SJW can just become 'anything I disagree with or don't understand'. This results in a belief that SJW thought rules sections of the Western World and is quickly taking everything over. Professors and scientists are frequently called SJWs, and there is a mass anti-intellectual movement now which declares college education to be 'SJW brainwashing' (arts and humanities subjects in particular). Even if you did not think that a particular topic had anything much to do with politics, someone will be more than happy to declare that SJWs must be involved.
As for the worst of it, and this is a very natural evolution of the previous belief, SJWs are part of a great and terrible worldwide conspiracy. Believers tend to edge dangerously close to National Socialism, believing that the Jewish elite are pulling the strings of the entire world. The Jewish elite means celebrities, politicians, businessmen, and bankers, which is odd when one considers that anti-fascist and communist movements are also supposed to be part of their big SJW plan. Often, world Communism is the actual end goal of the conspiracy, and that's why 'Cultural Marxism' is such a popular term. People are quick to point out that many Bolsheviks and many Frankfurt School thinkers were Jewish, unaware of what Communism actually means for bankers and the like. This anti-semitic folie a deux clearly arises from the Alt-Right's shared cuckold fetish, which is a very interesting social phenomenon that is probably worth some real examination by someone. They fixate on 'race mixing' and women's rights, spending inordinate amounts of time thinking about how they are unable to provide sexual competition in a world where borders are open and women can choose.
A minority of people will call themselves Social Justice Warriors, but they do not identify as SJWs before they or something they believe in has been called SJW as an insult. They want to show that just being insulted is not going to change their views, and that they still believe in one of the thousand different things they may have been called an SJW for believing. Though it may be noble to stand firm in one's beliefs, it still cannot be said that they add anything to make the term useful. Social Justice Warriors still does not refer to anything more specific than 'progressivism', and it still aids the people who use the term as a negative concept in their goal of generalizing people to drown out debate.