Civil law. One who becomes security for the debt of another, promising to pay it in case the principal does not do so. A surety; one bound for another, conjointly with him; a guarantor. He differs from a co-obligor in this, that the latter is equally bound to a debtor with his principal, while the former is not liable until the principal has failed to fulfill his engagement. The obligation of the fide-jussor was an accessory contract, for, if the principal obligation was not previously contracted, his engagement then took the name of mandate.
Cautioner. This kind of cautioner could be added to any contract, and his obligation transmitted against his heirs. It was different with the adpromissor.