Dictionary.com
Thesaurus.com

mesocratic

American  
[mez-uh-krat-ik, mes-, mee-zuh-, -suh-] / ˌmɛz əˈkræt ɪk, ˌmɛs-, ˌmi zə-, -sə- /

adjective

Petrology.
  1. (of an igneous rock) composed of light and dark minerals in nearly equal amounts.


mesocratic British  
/ ˌmɛsəˈkrætɪk /

adjective

  1. (of igneous rocks) containing 30–60 per cent of ferromagnesian minerals

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of mesocratic

First recorded in 1855–60; meso- + -crat + -ic