What does the word grindstone mean?

Usage examples for grindstone

  1. A throng of men and women crowded round a grindstone. – The World's Greatest Books, Vol III by Arthur Mee and J.A. Hammerton, Eds.
  2. And yet the entire commissioned force felt that they were being kept at the grindstone because of the frivolity of these few youngsters, and they did not like it. – The Deserter by Charles King
  3. She declared she heard some one turning the grindstone. – Under Padlock and Seal by Charles Harold Avery