To be completely honest, I not completely comfortable with the title, but it the one that Mike gave me. When I told my in-laws that I was leaving my job at IBM to become an "Eclipse Evangelist", they looked at me with that odd sort of open-mouthed look that is normally accompanied by the words "you're doing what?" My wife's family is very involved in the church; several of them actually have the title of "Evangelist" themselves. Indeed, there appears to be no dictionary definition of the term that doesn have something to do with the church.
According to Wikipedia, "the word evangelist comes from the Koine Greek word ('eu-angelos'), meaning bringer of good news." I can live with this definition. As an "Eclipse Evangelist", I see it as my job to comment on all the goodness that's happening in the Eclipse community. That's not to say that I won't ever comment on things that I think need improvement, because I think the community benefits from balance and honesty.