The Collaborative International Dictionary of English v.0.48:

idealisation \idealisation\ n.
   1. Same as idealization.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

idealisation
    n 1: (psychiatry) a defense mechanism that splits something you
         are ambivalent about into two representations--one good and
         one bad [syn: idealization, idealisation]
    2: something that exists only as an idea [syn: idealization,
       idealisation]
    3: a portrayal of something as ideal; "the idealization of rural
       life was very misleading" [syn: idealization,
       idealisation, glorification]