Source : Webster's Revised Unabridged Dictionary (1913)

Revivalist \Re*viv"al*ist\, n.
   A clergyman or layman who promotes revivals of religion; an
   advocate for religious revivals; sometimes, specifically, a
   clergyman, without a particular charge, who goes about to
   promote revivals. Also used adjectively.

Source : WordNet®

revivalist
     n : a preacher of the Christian gospel [syn: {evangelist}, {gospeler},
          {gospeller}]