Culet

noun

1. The small flat face at the bottom of a gem cut as a brilliant.
2. Armor consisting of overlapping plates used to protect the buttocks.
3. In armor, that part which protects the body behind, from the waist down.
4. In jewelry, the small flat surface at the back or bottom of a brilliant. Also called cullet, collet, and lower table. See cut under brilliant.
5. A component of armor, consisting of overlapping plates designed to protect the buttocks.