The Collaborative International Dictionary of English v.0.48:

Assuring \As*sur"ing\, a.
   That assures; tending to assure; giving confidence. --
   As*sur"ing*ly, adv.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Assure \As*sure\, v. t. [imp. & p. p. Assured; p. pr. & vb. n.
   Assuring.] [OF. ase["u]rer, F. assurer, LL. assecurare; L.
   ad + securus secure, sure, certain. See Secure, Sure, and
   cf. Insure.]
   1. To make sure or certain; to render confident by a promise,
      declaration, or other evidence.
      [1913 Webster]

            His promise that thy seed shall bruise our foe . . .
            Assures me that the bitterness of death
            Is past, and we shall live.           --Milton.
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   2. To declare to, solemnly; to assert to (any one) with the
      design of inspiring belief or confidence.
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            I dare assure thee that no enemy
            Shall ever take alive the noble Brutus. --Shak.
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   3. To confirm; to make certain or secure.
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            And it shall be assured to him.       --Lev. xxvii.
                                                  19.
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            And hereby we know that we are of the truth, and
            shall assure our hearts before him.   --1 John iii.
                                                  19.
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   4. To affiance; to betroth. [Obs.] --Shak.
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   5. (Law) To insure; to covenant to indemnify for loss, or to
      pay a specified sum at death. See Insure.
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   Syn: To declare; aver; avouch; vouch; assert; asseverate;
        protest; persuade; convince.
        [1913 Webster]

WordNet (r) 3.0 (2006):

assuring
    adj 1: giving confidence