Source : Webster's Revised Unabridged Dictionary (1913)

Evangelist \E*van"gel*ist\, n. [F. ['e]vang['e]liste, L.
   evangelista, fr. Gr. ?.]
   A bringer of the glad tidings of Church and his doctrines.
   Specially:
   (a) A missionary preacher sent forth to prepare the way for a
       resident pastor; an itinerant missionary preacher.
   (b) A writer of one of the four Gospels (With the definite
       article); as, the four evangelists, Matthew, Mark, Luke,
       and John.
   (c) A traveling preacher whose efforts are chiefly directed
       to arouse to immediate repentance.

             The Apostles, so far as they evangelized, might
             claim the tittle though there were many evangelists
             who were not Apistles.               --Plumptre.

Source : WordNet®

evangelist
     n 1: a preacher of the Christian gospel [syn: {revivalist}, {gospeler},
           {gospeller}]
     2: (when capitalized) any of the spiritual leaders who are
        assumed to be authors of the Gospels in the New Testament:
        Matthew, Mark, Luke, and John