A derivative with a payoff that is based on a swap rate of a specific maturity. For example, while a regular floating rate note might pay semi-annual coupons based on semi-annual fixings of 6-month USD LIBOR, a CMS note might pay semi-annual coupons based on semi-annual fixings of the 10-year semi-annual swap rate. Note, however, that the coupon frequency need not match that of the underlying swap rate: the note might pay semi-annual coupons based on fixings of the 10-year annual swap rate, for example.