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]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "revivalist":
   adorer, beadsman, celebrant, chapelgoer, churchgoer, colporteur,
   communicant, congregation, daily communicant, evangelist, idolater,
   missionary, missionary apostolic, missionary rector, missioner,
   petitioner, prayer, suppliant, supplicant, supplicator, venerator,
   votary, worshiper