n. Certainty; indubitableness: especially in the phrase of a surety, certainly, indubitably.n. Security; safety.n. That which makes sure, firm, or certain; foundation of stability; ground of security.n. Security against loss or damage; security for payment or for the performance of some act.n. One who has made himself responsible for another; specifically, in law, one who has bound himself with or for another who remains primarily liable; one who has contracted with the creditor or claimant that he will be answerable for the debt, default, or miscarriage of another; one who enters into a bond or recognizance or other obligation to answer for another's appearance in court, or for his payment of a debt or his performance of some act, and who, in case of the principal's failure, can be compelled to pay the debt or damages; a bondsman; a bail.n. Hence A sponsor.To act as surety for; guarantee; be bail or security for.