unbaptize

From un- +‎ baptize.

unbaptize (third-person singular simple present unbaptizes, present participle unbaptizing, simple past and past participle unbaptized)

1. (transitive) To undo the process of baptism for (someone).
   • 1817, Robert Southey, chapter XXIII, in History of Brazil, 2nd part, London: […] [William Pople] for Longman, Hurst, Rees, Orme, and Brown, […], →OCLC, page 296:

     Niezu soon arrived to enjoy his triumph, and unbaptize the children of the Reduction. This curious ceremony was performed by washing the head with hot water, rubbing sand upon the tongue, and scraping it with a shell, to bring clean away any remains of the salt with which it had been touched; […]