Definition of superstrate in US English:

superstrate

noun

  • 1Superstratum; specifically an overlying or outer layer of transparent rigid material, as on the sunward side of a photovoltaic cell.

  • 2Linguistics. A language or aspect of a language, typically belonging to a colonizing or dominant group, which affects another socially and culturally dominated language and contributes to the formation of a Creole, especially in providing the lexicon.

Origin

1930s. Alteration of superstratum, after substrate.