What does the word treadmill mean?

Usage examples for treadmill

  1. The forest was a great treadmill in which men toiled all day, only to be surrounded at night by the same grandeurs and littlenesses they had that morning left. – The Silent Places by Steward Edward White
  2. Otherwise I could accept the ox- routine and grind out my soul in the treadmill of three meals a day. – Neighbours by Robert Stead
  3. And in this view, though our efforts be humble and our toil hard, life can never be a treadmill. – Words of Cheer for the Tempted, the Toiling, and the Sorrowing by T. S. Arthur