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.
A medieval Slavic state that was the forerunner of modern Russia. Centered around the city of Kiev, it included most of present-day Ukraine and Belarus and part of northwest Russia. Kievan power and influence grew steadily through the 10th and 11th century, but was later weakened by internal disputes and fell to the Mongols by 1240.