A more thorough explanation:

Definition: Exhausted-combination rejection is a type of rejection in patent law. It occurs when a patent claim is rejected because all the elements of the invention perform the same function as a previously patented invention, even if one or more elements perform in a different way. This type of rejection is also known as old-combination rejection.

Example: Suppose an inventor applies for a patent on a new type of car engine. The patent examiner finds that all the elements of the engine perform the same function as a previously patented engine, even though some elements perform in a different way. The examiner may issue an exhausted-combination rejection, stating that the combination of elements is not patentable because it has already been patented.

This example illustrates how exhausted-combination rejection works in patent law. Even if an inventor comes up with a new way of doing something, if the overall function is the same as a previously patented invention, the combination may not be patentable.