The Collaborative International Dictionary of English v.0.48:

Supercilious \Su`per*cil"i*ous\, a. [L. superciliosus, fr.
   supercilium an eyebrow, pride; super over, + cilium an
   eyelid; probably akin to celare to conceal. Cf. Conceal.]
   Lofty with pride; haughty; dictatorial; overbearing;
   arrogant; as, a supercilious officer; asupercilious air;
   supercilious behavior. -- Su`per*cil"i*ous*ly, adv. --
   Su`per*cil"i*ous*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

superciliousness
    n 1: the trait of displaying arrogance by patronizing those
         considered inferior [syn: condescension,
         superciliousness, disdainfulness]