A contract which allows investors to lock in a preset swap spread for a deferred started swap. In a forward swap, the fixed rate payer would get a certain maximum spread over a given benchmark index (such as Treasury rate). On the opposite leg, the fixed rate receiver would get a certain minimum spread over the benchmark. A payer (receiver) spreadlock allows the holder to enter into a swap whereby it pays (receives) the benchmark plus the agreed spread.

It is also known as a deferred rate setting swap.