Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio.
the work to which a person's life is devoted; most important work of one's life
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.
The chief or entire work of a person's lifetime.