grit 
(grĭt)
(grĭt)n.
1. Minute rough granules, as of sand or stone.
2. The texture or fineness of sand or stone used in grinding.
3. A coarse hard sandstone used for making grindstones and millstones.
4. Informal Indomitable spirit; pluck.
v. grit·ted, grit·ting, grits
v.tr.
1. To clamp (the teeth) together.
2. To cover or treat with grit.
v.intr.
To make a grinding noise.
[Middle English gret, sand, from Old English grēot.]