Source : Webster's Revised Unabridged Dictionary (1913)

Imperious \Im*pe"ri*ous\, a. [L. imperiosus: cf. F.
   imp['e]rieux. See {Imperial}.]
   1. Commanding; ascendant; imperial; lordly; majestic. [Obs.]
      ``A vast and imperious mind.'' --Tilloison.

            Therefore, great lords, be, as your titles witness,
            Imperious.                            --Shak.

   2. Haughly; arrogant; overbearing; as, an imperious tyrant;
      an imperious manner.

            This imperious man will work us all From princes
            into pages.                           --Shak.

            His bold, contemptuous, and imperious spirit soon
            made him conspicuous.                 --Macaulay.

   3. Imperative; urgent; compelling.

            Imperious need, which can not be withstood.
                                                  --Dryden.

   Syn: Dictatorial; haughty; domineering; overbearing; lordly;
        tyrannical; despotic; arrogant; imperative;
        authoritative; commanding; pressing.

   Usage: {Imperious}, {Lordly}, {Domineering}. One who is
          imperious exercises his authority in a manner highly
          offensive for its spirit and tone; one who is lordly
          assumes a lofty air in order to display his
          importance; one who is domineering gives orders in a
          way to make other feel their inferiority.

Source : WordNet®

imperious
     adj : able to deal authoritatively with affairs; "dismissed the
           matter with an imperious wave of her hand" [syn: {masterful}]