/gruynd"stohn'/ , n.
1. a rotating solid stone wheel used for sharpening, shaping, etc.
2. a millstone.
3. keep or put one's nose to the grindstone , to work, study, or practice hard and steadily or to cause someone to do so: If I put my nose to the grindstone, I'll finish the job this week.
[ 1175-1225; ME. See GRIND, STONE ]