The Collaborative International Dictionary of English v.0.48:

Secularization \Sec`u*lar*i*za"tion\, n. [Cf. F.
   s['e]cularisation.]
   The act of rendering secular, or the state of being rendered
   secular; conversion from regular or monastic to secular;
   conversion from religious to lay or secular possession and
   uses; as, the secularization of church property.
   [1913 Webster]

WordNet (r) 3.0 (2006):

secularization
    n 1: the activity of changing something (art or education or
         society or morality etc.) so it is no longer under the
         control or influence of religion [syn: secularization,
         secularisation]
    2: transfer of property from ecclesiastical to civil possession
       [syn: secularization, secularisation]