Source : Webster's Revised Unabridged Dictionary (1913)

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.

            His promise that thy seed shall bruise our foe . . .
            Assures me that the bitterness of death Is past, and
            we shall live.                        --Milton.

   2. To declare to, solemnly; to assert to (any one) with the
      design of inspiring belief or confidence.

            I dare assure thee that no enemy Shall ever take
            alive the noble Brutus.               --Shak.

   3. To confirm; to make certain or secure.

            And it shall be assured to him.       --Lev. xxvii.
                                                  19.

            And hereby we know that we are of the truth, and
            shall assure our hearts before him.   --1 John iii.
                                                  19.

   4. To affiance; to betroth. [Obs.] --Shak.

   5. (Law) To insure; to covenant to indemnify for loss, or to
      pay a specified sum at death. See {Insure}.

   Syn: To declare; aver; avouch; vouch; assert; asseverate;
        protest; persuade; convince.

Assuring \As*sur"ing\, a.
   That assures; tending to assure; giving confidence. --
   {As*sur"ing*ly}, adv.

Source : WordNet®

assuring
     adj : giving confidence