Noun
A flat, circular stone, revolving on an axle, for grinding or sharpening tools, or shaping or smoothing objects.
Source: Webster's dictionaryThen you must tell 'em dat love ain't somethin' lak uh grindstone dat's de same thing everywhere and do de same thing tuh everything it touch. Love is lak de sea. It's uh movin' thing, but still and all, it takes its shape from de shore it meets, and it's different with every shore. Zora Neale Hurston
Hold their noses to the grindstone. Thomas Middleton
And hold one another's noses to the grindstone hard. Robert Burton
Keep your nose to the grindstone. Danish Proverb
I shall hold his Nose to the Grindstone. Scottish Proverb
He does not live in this world that can skin a grindstone. Danish Proverb