A social justice warrior (SJW) is a sad existence whose only goal is to push nonsensical agendas, they're mostly active on the internet and usually engage in attacks against healthy normal individuals or entire communities. Their most usual arguments are unsupported claims of misogyny, especially against white male man. Even though they proclaim to be on the side of justice they have no problem with being racist and/or sexist.
Another mark of SJWs is their persecution complex that makes them agree with everything said that makes them feel sorry about their ethnic background or gender, even if it is factually wrong.
Popular SJW websites related to #GamerGate include Kotaku and Polygon.
Common SJW phrases:
"muh soginy" - when faced with any argument they can't properly disprove.
"straight white males can't see sexism" - even when they themselves are straight white males and/or practicing sexism.
"the patriarchy" - a fictional social construct the SJWs believe in; supposedly rules over society and has only the goal of making straight white male feel empowered over anyone else.