A swap that gives one of the counterparties (or sometimes both) the right to terminate the contract prior to maturity, at one or more predetermined dates, or under predetermined conditions.
In a plain vanilla swap, the term callable swap is used when the right to terminate the contract is given to the fixed-rate payer (the swap purchaser), and the term putable swap or puttable swap is used when the right to terminate the contract is given to the floating-rate payer (the swap seller).