An interest rate swap that enables the client to pay a rate that is lower than that of a vanilla swap in return for the right given by the client to the swap dealer to switch his payments from fixed to floating or floating to fixed at some point during the tenor of the swap. This swap is similar to a callable swap except that the terms of the swap are changed rather than terminated. For example, the swap dealer may have the right to switch a floating leg to a fixed leg at his own discretion. This swap differs from a trigger swap in that in the former the change of terms is discretionary, whereas it is specified in the case of the latter.