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]