The Collaborative International Dictionary of English v.0.48:

Minimization \Min`i*mi*za"tion\, n.
   The act or process of minimizing. --Bentham.
   [1913 Webster]

WordNet (r) 3.0 (2006):

minimization
    n 1: the act of reducing something to the least possible amount
         or degree or position [syn: minimization, minimisation]
         [ant: maximation, maximisation, maximization]