The chief or entire work of a person's lifetime.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "lifework" in a sentence
"A lifework is given true substance and value only by the vital individual who puts his life into the struggle."
"His lifework is The Magic Door, a sequence, written over a period of some 35 years."
"So several potential honorees had their lifework duly poked, prodded and manhandled, separating the sf from the fantasy."