The Collaborative International Dictionary of English v.0.48:

defrock \defrock\ v. t.
   To divest of the frock, i. e. to deprive (a priest, minister,
   etc.) of official ecclesiastical authority; -- of church
   officials.

   Syn: unfrock.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

defrock
    v 1: divest of the frock; of church officials [syn: defrock,
         unfrock]

Moby Thesaurus II by Grady Ward, 1.0:

77 Moby Thesaurus words for "defrock":
   boot, bounce, break, bring into discredit, bring low,
   bring shame upon, bump, bust, can, cashier, cast reproach upon,
   debase, deconsecrate, degrade, demote, deplume, depose, deprive,
   dethrone, disbar, discharge, discredit, discrown, disemploy,
   disenthrone, disgrace, dishonor, dismiss, displace, displume,
   drum out, excommunicate, expel, fire, furlough, give the ax,
   give the gate, humiliate, impute shame to, kick, kick upstairs,
   lay off, let go, let out, liquidate, make redundant, oust,
   overthrow, pension, pension off, pillory, purge, put to shame,
   read out of, reflect discredit upon, release, remove,
   remove from office, replace, reproach, retire, sack,
   separate forcibly, shame, strip, strip of office, strip of rank,
   superannuate, surplus, suspend, turn off, turn out, unchurch,
   unfrock, unsaddle, unseat, unthrone