metalanguage

metakieli puhekieltä Any language or vocabulary of specialized terms used to describe or analyze a language or linguistic process.
2005, Michael Cronin, Training for the New Millennium: Pedagogies for translation and interpreting, edited by Martha Tennent, Benjamins Translation Library, p. 255:

In order to talk or theorise about phenomena, one inevitably uses a language that is in effect a metalanguage, a special instance of language that allows the theorist to stand back and describe what is happening.