Wiktionary
n. A theory about a theory.
Wikipedia
A metatheory or meta-theory is a theory whose subject matter is some theory. All fields of research share some meta-theory, regardless whether this is explicit or correct. In a more restricted and specific sense, in mathematics and mathematical logic, metatheory means a mathematical theory about another mathematical theory.
The following is an example of a meta-theoretical statement:
Meta-theoretical investigations are generally part of philosophy of science. Also a metatheory is an object of concern to the area in which the individual theory is conceived.
Usage examples of "metatheory".
And he even began work on this -- put together a dictionary, a syntax, set up rules of transposition, categories, hierarchies, a sort of metatheory of types semantically extended -- but then he saw that the task was an empty game not worth the effort, for nothing resulted from it but the possibility of generating those networks, checkerboards, edifices -- those crystal palaces, if you like -- built of words.