The Collaborative International Dictionary of English v.0.48:

Anti-Semitism \An`ti-Sem"i*tism\, n.
   Opposition to, or hatred of, Semites, esp. Jews. The word is
   sometimes also applied to acts motivated by or evincing
   antisemitism. -- An`ti-Sem"ite, n. -- An`ti-Sem*it"ic, a.
   [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

antisemitism
    n 1: the intense dislike for and prejudice against Jewish people
         [syn: anti-Semitism, antisemitism]