I'll assume most of us know about cross-validation and are accustomed to using Training and Test sets. However, I've also seen references to a third set that you use to test a completed model. It's the test to see how your model does against a dataset that it hasn't seen before; helps determine if your model has been overly-fit to the training data.
I have seen this dataset referred to everything from "the third dataset", "the wild dataset", "the real-world dataset". So what is the appropriate name for this third dataset?