The Collaborative International Dictionary of English v.0.48:

Disestablish \Dis`es*tab"lish\, v. t.
   To unsettle; to break up (anything established); to deprive,
   as a church, of its connection with the state. --M. Arnold.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disestablish
    v 1: deprive (an established church) of its status