evangelist

Short definition from Wiktionary

Noun

1. 1
   An itinerant or special preacher, especially a revivalist, who conducts services in different cities or locations, now often televised.
2. 2
   A writer of a gospel, especially the four New Testament Gospels (Matthew, Mark, Luke, and John), usually capitalized (Evangelist).
3. 3
   A person who first brought the gospel to a city or region.
4. 4
   A patriarch.
5. 5
   A person marked by extreme enthusiasm for or support of any cause, particularly with regard to religion.
6. 6
   A person hired to promote a particular technology.
7. 7
   A writer of a gospel, especially the four New Testament Gospels (Matthew, Mark, Luke, and John), (also evangelist.)