Definition from Nolo’s Plain-English Law Dictionary
A will that is completed, signed, and sealed in secret. The will maker delivers the sealed document to a notary public along with a signed statement that the document is a valid will. In front of witnesses, the notary records on the envelope the circumstances of the transaction, then the notary and witnesses sign the envelope. Mystic wills are valid only in the state of Louisiana under certain circumstances. Also called a secret will, sealed will, or closed will.