indefatigable

• Joan of Arc was indefatigable, and with her keen eye sought out the likeliest place where an assault might be successfully carried; but she lacked troops for storming such strong outworks as Paris then had. —  Joan of Arc
• Thus I passed a portion of the night; my professor was indefatigable, and, for my part, I was not weary of listening. —  Memoirs of Robert-Houdin
• My appetite for books was as ample and indiscriminating as it was indefatigable, and I since have had too frequently reason to repent that few ever read so much, and to so little purpose Among the valuable acquisitions I made about this time was an acquaintance with Tasso's Jerusalem Delivered, through the flat medium of Mr. Hoole's translation. —  Memoirs of the Life of Sir Walter Scott, Volume I (of 10)
• Nurse was indefatigable--a miracle of energy and resource--but through all her anxiety and tenderness for the little patient, it was impossible not to recognise the keen professional zest in a "good case Give me a bad pneumonia, and I'm happy!" —  The Lady of the Basement Flat
• His labors in this department were indefatigable, and many of the most important and successful movements of the war originated with him. —  Hidden Treasures Or, Why Some Succeed While Others Fail

Roget's II: The New Thesaurus

Used in the Same Context