asserter

from WordNet (r) 3.0 (2006)

asserter
    n 1: someone who claims to speak the truth; "a bold asserter";
         "a declarer of his intentions"; "affirmers of traditional
         doctrine"; "an asseverator of strong convictions"; "an
         avower of his own great intelligence" [syn: {asserter},
         {declarer}, {affirmer}, {asseverator}, {avower}]

from The Collaborative International Dictionary of English v.0.48

Asserter \As*sert"er\, n.
   One who asserts; one who avers pr maintains; an assertor.
   [1913 Webster]

         The inflexible asserter of the rights of the church.
                                                  --Milman.
   [1913 Webster]