SJW's generally don't care about definitions, unless they are dishonestly using them as an absolute authority to dodge responsibility for their actions.
For example, the same feminists who demand special privileges and advocate for female supremacy will immediately pull out a dictionary and declare the feminism is a movement for egalitarianism.
To me, SJWs are largely the under-30 liberals who have no sense of personal responsibility, who are so deeply immersed in the an ideology of identity politics they function like a cult, who are intolerant of anyone elses opinion, who are against free speech, who think bullying is fine as long as its done by the right side, who lack a sense of meaning and purpose in life and so invest all of their self worth and sense of purpose in their extremist political/social views, and who eagerly, shamelessly participate in grouthink.
SJWs have ruined feminism and they both started and ruined the Black Lies Matters movement.
But wikipedia has, perhaps, a more useful explanation. Remember, this is NOT about 'equal rights for women' nor is it about 'civil rights', nor is it about a 'positive, functional approach to multiculturalism'. That's the facade, the self deception they engage in:
"Social justice warrior" (commonly abbreviated SJW) is a pejorative term for an individual promoting socially progressive views,[1] including feminism,[1][2] civil rights,[1] multiculturalism,[1] and identity politics.[3] The accusation of being an SJW carries implications of pursuing personal validation rather than any deep-seated conviction,[4] and being engaged in disingenuous social justice arguments or activism to raise personal reputation, also known as virtue signalling.[5]"
Exactly!