The best replacement for believer is disciple.

The best alternatives to believer are rated as following:
★★★★★  disciple
★★★  follower
★★  non believer
★★  atheist
★★  unbeliever
★  skeptic
★  american history x
★  chosen
  belieber
  at first sight
  believer
  nonbeliever

Your alternative for believer is not listed? Suggest!
Speaking about believer, one probably shouldn't forget about unbeliever.

Other search terms related to believer and their ratings are:
★★★★★ unbeliever
You have in mind a companion for believer and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of believer in all years. Click on graph for more.
believer
disciple
follower