indefatigable
adjective in·de·fat·i·ga·ble \ˌin-di-ˈfa-ti-gə-bəl\
incapable of being tired out; not yielding to fatigue; untiring.
Citations for indefatigable
Colonel Cathcart was indefatigable that way, an industrious, intense, dedicated military tactician who calculated day and night in the service of himself.
Joseph Heller, Catch-22, 1961
I am, perhaps, giving the impression that nothing practical was being done in the way of investigations. On the contrary, Scotland Yard and the local police of the various counties were indefatigable in following up the smallest clues.
Agatha Christie, The ABC Murders, 1936
Origin of indefatigable
Indefatigable entered English in the late 1500s and finds its roots in the Latin term defatīgāre meaning "to tire out."
