Definition of mesostasis in English:

mesostasis

noun

Geology
  • The most recently formed interstitial substance (whether glassy or cryptocrystalline) in an igneous rock.

Origin

Late 19th century; earliest use found in Nature: a weekly journal of science. From meso- + ancient Greek στάσις.

Pronunciation

mesostasis

/mɪˈsɒstəsɪs/