1. The formal pledge by which a person becomes a surety.
2. Int’l law. An ultra vires promise of an official agent (such as a general in wartime), requiring later ratification by the principal.
3. Roman law. A form of guarantee accessory to an oral contract. • Only Roman citizens could make this type of guarantee. See ADPROMISSION(1). — sponsional (spon-sh[schwa]n-[schwa]l), adj.