The Collaborative International Dictionary of English v.0.48:

Catholicize \Ca*thol"i*cize\, v. t. & i.
   To make or to become catholic or Roman Catholic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

catholicize
    v 1: cause to adopt Catholicism [syn: catholicize,
         catholicise, latinize, latinise]