The Collaborative International Dictionary of English v.0.48:

Averment \A*ver"ment\, n. [Cf. OF. averement, LL. averamentum.
   See Aver, v. t.]
   1. The act of averring, or that which is averred;
      affirmation; positive assertion.
      [1913 Webster]

            Signally has this averment received illustration in
            the course of recent events.          --I. Taylor.
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   2. Verification; establishment by evidence. --Bacon.
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   3. (Law) A positive statement of facts; an allegation; an
      offer to justify or prove what is alleged.
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   Note: In any stage of pleadings, when either party advances
         new matter, he avers it to be true, by using this form
         of words: "and this he is ready to verify." This was
         formerly called an averment. It modern pleading, it is
         termed a verification. --Blackstone.
         [1913 Webster] Avernal

WordNet (r) 3.0 (2006):

averment
    n 1: a declaration that is made emphatically (as if no
         supporting evidence were necessary) [syn: assertion,
         averment, asseveration]