One who makes or gives a guaranty; a warrantor; a surety.
A person who provides a guarantee to a lender that the person borrowing the money on a mortgage will meet their commitment. In the event that the borrower defaults it is ultimately the responsibility of the guarantor to meet the mortgage payments. Generally lenders do not like this arrangement.
A person who provides a written statement of agreement to pay the rent in the event that the primary renter fails to do so.