grit

ot noun

1. A collection of hard small materials, such as dirt, ground stone, debris from sandblasting or other such grinding, or swarf from metalworking. The flower beds were white with grit from sand blasting the flagstone walkways.
2. Inedible particles in food. These cookies seem to have grit from nutshells in them.
3. A measure of the relative coarseness of an abrasive material such as sandpaper, the smaller the number the coarser the abrasive. I need a sheet of 100 grit sandpaper.
4. Strength of mind; great courage or fearlessness; fortitude. That kid with the cast on his arm has the grit to play dodgeball.

fe’l verb

1. Apparently only in grit one's teeth: to clench, particularly in reaction to pain or anger. He has a sleeping disorder and grits his teeth.
2. To cover with grit.
3. To give forth a grating sound, like sand under the feet; to grate; to grind.