abjurer
n. C2 Proficiency ab·jur·er
n. a person who officially gives up a belief or a right. This is a very formal word used in legal or religious contexts.
n. a person who formally renounces a belief, a right, or a privilege. Often used in legal or ecclesiastical contexts to describe the act of relinquishing a claim or doctrine.
The abjurer signed the document to give up his title.
The abjurer stood before the court to formally renounce his allegiance to the former regime.
Historical records detail the abjurer who, under threat of execution, publicly recanted his heretical views to the assembled clergy and nobility.
From abjure + -er.