Abjuration is solemn repudiation, denial, abandonment, or renunciation by or upon oath. It is often the renunciation of citizenship or some other right or privilege. In common religious language this term is restricted to the renunciation of heresy made by the repenting heretic on the occasion of his reconciliation with the Church.
The act of Congress of the 14th of April, 1802, 2 Story's Laws, U.S. 850, requires that when an alien shall apply to be admitted a citizen of the United States, he shall declare on oath or affirmation before the court where the application shall be made, that he absolutely and entirely renounce and abjure all allegiance and fidelity which he owes to any foreign prince, and particularly, by name, the prince, whereof he was before a citizen or subject.
In England, an oath of abjuration was taken by members of Parliament, clergy, and laymen, pledging to support the current British monarch and repudiated the right of the Stuarts and other claimants to the throne.