Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio.
noun pl. diarchies
government shared by two rulers, powers, etc.
Origin: di- plush -archy
Used by arrangement with John Wiley & Sons, Inc.
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
also dy·ar·chynoun pl. di·ar·chies also dy·ar·chies
Government by two joint rulers.