Definition
incapable or seemingly incapable of being tired out; not giving way to fatigue; untiring.
Main Example
"Strong willed! Shrewd! Indefatigable!" These are some of the words being used by noted political analysts to describe the two new party leaders in the House: Republican Tom DeLay and Democrat Nancy Pelosi. Expect bold and imaginative maneuvers from these two quintessential politicians as major legislative battles draw near.
Workplace
Examples
While many people can be credited for our recent successes, I would especially like to mention Jerry. He was indefatigable in leading our efforts to capture the No. 1 position in Fortune magazine's annual survey.
If only I could get some of Carolyn's DNA transferred into me. She can work 24 hours a day, 365 days a year, and never run out of steam. She is indefatigable!
Other
Examples
your calling someone "an indefatigable optimist" because he or she, in spite of numerous setbacks, remains as enthusiastic as ever
the late Mother Teresa who indefatigably pursued her objective of providing a shelter for Calcutta's destitute
recent Nobelist and former President Jimmy Carter being an indefatigable supporter of human rights and working indefatigably for world peace