Passive Activism

What defines an "activist"?

We always hear the word in association with people who attend demonstrations and wave signs ("union activist," "pro-life activist"), or referring to public advocates for a cause. But what exactly makes a person an "activist"? A full-time advocate of a cause is an activist; what about a part-time advocate? What about someone who works on advocating it for an hour a week? Are they activists too? Clearly, someone who sympathizes with a cause but does nothing about it is not an activist, yet someone who attends one protest is; where do we draw the line? How many hours a week do you have to put in before you are an "activist"?

And what about people who work for causes that don't have a ribbon color assigned to them? What about, say, people who are passionate about math education and provide free tutoring? What about people who are passionate about good parenting and spend all their time quietly raising their children? Are they activists too?

Are we all, in some sense, passive activists?