The Collaborative International Dictionary of English v.0.48:

Discourteous \Dis*cour"te*ous\ (?; see Courteous, 277), a.
   [Pref. dis- + courteous: cf. OF. discortois.]
   Uncivil; rude; wanting in courtesy or good manners;
   uncourteous. -- Dis*cour"te*ous*ly, adv. --
   Dis*cour"te*ous*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

discourteous
    adj 1: showing no courtesy; rude; "a distant and at times
           discourteous young" [ant: courteous]
    2: lacking social graces [syn: discourteous, ungracious]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "discourteous":
   abrupt, aweless, boorish, brusque, curt, derisive, disparaging,
   disrespectful, ill-bred, ill-mannered, impertinent, impolite,
   impudent, inaffable, insolent, irreverent, misbehaved, ridiculing,
   rude, short, unaccommodating, uncivil, uncomplaisant, uncourteous,
   uncourtly, ungallant, ungentlemanly, ungracious, unladylike,
   unmannerly, unpolite