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]