Source : Webster's Revised Unabridged Dictionary (1913)

Assume \As*sume"\, v. t. [imp. & p. p. {Assumed}; p. pr. & vb.
   n. {Assuming}.] [L. assumere; ad + sumere to take; sub +
   emere to take, buy: cf. F. assumer. See {Redeem}.]
   1. To take to or upon one's self; to take formally and
      demonstratively; sometimes, to appropriate or take
      unjustly.

            Trembling they stand while Jove assumes the throne.
                                                  --Pope.

            The god assumed his native form again. --Pope.

   2. To take for granted, or without proof; to suppose as a
      fact; to suppose or take arbitrarily or tentatively.

            The consequences of assumed principles. --Whewell.

   3. To pretend to possess; to take in appearance.

            Ambition assuming the mask of religion. --Porteus.

            Assume a virtue, if you have it not.  --Shak.

   4. To receive or adopt.

            The sixth was a young knight of lesser renown and
            lower rank, assumed into that honorable company.
                                                  --Sir W.
                                                  Scott.

   Syn: To arrogate; usurp; appropriate.

Assuming \As*sum"ing\, a.
   Pretentious; taking much upon one's self; presumptuous.
   --Burke.

Source : WordNet®

assuming
     adj : excessively forward; "an assumptive person"; "on a subject
           like this it would be too assuming for me to decide";
           "the duchess would not put up with presumptuous
           servants" [syn: {assumptive}, {presumptuous}]