What is the term for a formal legal document that revokes a previous will?

The term that refers to a formal legal document that revokes a previous will is "codicil." A codicil serves as an addendum or modification to an existing will, and it can explicitly state the intention to revoke parts or the entirety of the prior will. By creating a codicil, the testator (the person who made the will) can make changes or updates without having to draft a completely new will, while still ensuring that the revocation of the earlier document is clear and legally effective.

The other terms do not serve this purpose: an affidavit is a written statement confirmed by oath or affirmation used in legal proceedings; a trust is a fiduciary relationship where a trustee holds assets for the benefit of beneficiaries; and rescission is a legal term indicating the annulment or cancellation of a contract, which does not apply to the revocation of a will directly.