The study of the methods and aims of philosophy, consisting of a lot of questions that presuppose deeper questions in epistemology, philosophy of language, and other philosophical subdisciplines. Paradoxically, better done after one has explored a lot of philosophy, rather than before.
Philosophy of the 20th Century was characterized as being "talk about talk"--reflecting the natural language philosophy movement that received its main inspiration from the writings of G. E. Moore, Ludwig Wittgenstein, and J. L. Austin. Taking that perspective, metaphilosophy would be "talk about talk about talk." But this really just collapses back to "talk about (a certain type of) talk." So the regression wouldn't get very far, metaphilosophy would be seen as a subdomain of philosophy. Which is not to say that the term would have no potiential for use. Only that it references a subset, not a superset; not moving to "a higher philosophical level", just turning the ordinary level on itself.