The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

revivalist
    n 1: a preacher of the Christian gospel [syn: evangelist,
         revivalist, gospeler, gospeller]