affirmer
1. [ noun ] someone who claims to speak the truth
Synonyms: asseverator avower declarer asserter
Examples:

"a bold asserter" "a declarer of his intentions" "affirmers of traditional doctrine" "an asseverator of strong convictions" "an avower of his own great intelligence"

Related terms: communicator postulator declare affirm
Similar spelling:   affirm
  affirmed
  affirmable
  affirmatory
  affirmative
  affirmation