The floating rate that corresponds to the length of the stub period of a swap. The stub period usually begins on the date coupon payments begin to accrue and ends on the first payment date. The floating rate assigned to that shorter period is called the stub rate. And since many swaps are traded on interim dates, the existence of a stub rate for a single period is a required adjustment in so many contracts.

As far as futures contracts are concerned, stub rate refers to a prorated interest rate that corresponds to the period from the spot settlement to the end of the period covered by a futures contract. In other words, it is the interest rate from today to the expiration date of the first futures contract known as the front month contract.