Defrocking was the process of officially stripping a religious leader of the rights and privileges of their title.
In 2366, a then powerless, Human Q described himself to Jean-Luc Picard as defrocked. (TNG: "Deja Q")
In 2371, Vedek Yarka was defrocked, ostensibly for teachings contrary to the Bajoran religion. Odo had sources who claimed it was actually due to his leading protests against the Vedek Assembly regarding their endorsement of a peace treaty with Cardassia. (DS9: "Destiny")