The Collaborative International Dictionary of English v.0.48:

Disdainful \Dis*dain"ful\, a.
   Full of disdain; expressing disdain; scornful; contemptuous;
   haughty.
   [1913 Webster]

         From these
         Turning disdainful to an equal good.     --Akenside.
   -- Dis*dain"ful*ly, adv. -- Dis*dain"ful*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disdainful
    adj 1: expressing extreme contempt [syn: contemptuous,
           disdainful, insulting, scornful]
    2: having or showing arrogant superiority to and disdain of
       those one views as unworthy; "some economists are disdainful
       of their colleagues in other social disciplines"; "haughty
       aristocrats"; "his lordly manners were offensive"; "walked
       with a prideful swagger"; "very sniffy about breaches of
       etiquette"; "his mother eyed my clothes with a supercilious
       air"; "a more swaggering mood than usual"- W.L.Shirer [syn:
       disdainful, haughty, imperious, lordly,
       overbearing, prideful, sniffy, supercilious,
       swaggering]

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "disdainful":
   abjuratory, arrogant, audacious, bold, brash, brassy, brazen,
   bumptious, cavalier, challenging, cheeky, clannish, cliquish,
   cocky, cold, contemptuous, contumelious, cool, daring, declinatory,
   defiant, defying, derisive, despising, dismissive, disregardful,
   exclusive, familiar, forward, greatly daring, haughty,
   high and mighty, highfalutin, hoity-toity, hubristic, impertinent,
   impudent, insolent, insulting, jeering, lordly, mocking, obtrusive,
   overpresumptuous, overweening, pert, pompous, presuming,
   presumptuous, prideful, procacious, proud, pushy, regal,
   regardless of consequences, rejective, renunciative, saucy,
   scornful, sneering, sniffy, snobbish, snobby, snooty, snotty,
   stuck-up, supercilious, superior, toploftical, toplofty, uppish,
   uppity, withering