WordNet (r) 3.0 (2006):

rationalisation
    n 1: (psychiatry) a defense mechanism by which your true
         motivation is concealed by explaining your actions and
         feelings in a way that is not threatening [syn:
         rationalization, rationalisation]
    2: the cognitive process of making something seem consistent
       with or based on reason [syn: rationalization,
       rationalisation]
    3: (mathematics) the simplification of an expression or equation
       by eliminating radicals without changing the value of the
       expression or the roots of the equation [syn:
       rationalization, rationalisation]
    4: the organization of a business according to scientific
       principles of management in order to increase efficiency
       [syn: rationalization, rationalisation]
    5: systematic organization; the act of organizing something
       according to a system or a rationale [syn: systematization,
       systematisation, rationalization, rationalisation]