Definition of green schist in US English:

green schist

noun

Geology
  • A schist of a greenish colour; specifically (usually in form greenschist) a schistose or foliose rock with a greenish colour resulting from an abundance of chlorite, epidote, and albite, and formed by metamorphism of basic igneous rocks.

Origin

Early 19th century. From green + schist.

Pronunciation

green schist

/ˈɡriːn ˌʃɪst/