The meaning of this term depends on the context in which it is used:
A type of debt security (www.practicallaw.com/0-207-6955), typically a negotiable certificate evidencing a loan to the issuer by which the issuer promises to pay the holder its face value plus (usually) amounts of interest at future dates. For more on this type of bond, see Practice note, Bond issues: overview (www.practicallaw.com/4-201-8058).
A means of protection against non-performance used in domestic and international contracts. The issuer of the bond undertakes to be responsible for the fulfilment of a contractual obligation owed by one person to another if the first person defaults. May also be called a bank guarantee (www.practicallaw.com/9-200-1381). For more on this type of bond, see Practice note, Bonds, guarantees and standby credits: overview (www.practicallaw.com/4-107-3649).