asserter
1. [ noun ] someone who claims to speak the truth
Synonyms: asseverator avower declarer affirmer
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:   assert
  asserted
  assertive
  assertable
  assertion
  asserting
  assort
  assortment
  assertively
  assorted