The Collaborative International Dictionary of English v.0.48:

Arrogance \Ar"ro*gance\, n. [F., fr. L. arrogantia, fr.
   arrogans. See Arrogant.]
   The act or habit of arrogating, or making undue claims in an
   overbearing manner; that species of pride which consists in
   exorbitant claims of rank, dignity, estimation, or power, or
   which exalts the worth or importance of the person to an
   undue degree; proud contempt of others; lordliness;
   haughtiness; self-assumption; presumption.
   [1913 Webster]

         I hate not you for her proud arrogance.  --Shak.
   [1913 Webster]

   Syn: Haughtiness; hauteur; assumption; lordliness;
        presumption; pride; disdain; insolence; conceit;
        conceitedness. See Haughtiness.
        [1913 Webster]

WordNet (r) 3.0 (2006):

arrogance
    n 1: overbearing pride evidenced by a superior manner toward
         inferiors [syn: arrogance, haughtiness, hauteur,
         high-handedness, lordliness]