The Collaborative International Dictionary of English v.0.48:

Discourtesy \Dis*cour"te*sy\, n. [Pref. dis- + courtesy: cf. OF.
   descourtoisie.]
   Rudeness of behavior or language; ill manners; manifestation
   of disrespect; incivility.
   [1913 Webster]

         Be calm in arguing; for fierceness makes
         Error a fault, and truth discourtesy.    --Herbert.
   [1913 Webster]

WordNet (r) 3.0 (2006):

discourtesy
    n 1: an expression of lack of respect [syn: disrespect,
         discourtesy]
    2: a manner that is rude and insulting [syn: discourtesy,
       rudeness] [ant: courtesy, good manners]
    3: a lack of politeness; a failure to show regard for others;
       wounding the feelings or others [syn: discourtesy,
       offense, offence, offensive activity]

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "discourtesy":
   badness, correct deportment, courtesy, disesteem, dishonor,
   disorder, disorderliness, disorderly conduct, disparagement,
   disrespect, disrespectfulness, disruption, disruptiveness,
   etiquette, frowned-upon behavior, good behavior, good citizenship,
   good manners, hooliganism, horseplay, impropriety, impudence,
   insolence, irreverence, lack of respect, misbehavior, misconduct,
   misdemeanor, misdoing, naughtiness, nonsanctioned behavior,
   poor behavior, ridicule, roughhouse, rowdiness, rowdyism,
   ruffianism, sanctioned behavior, sociability, vandalism,
   venial sin, vice, wrongdoing