cab·o·chon 
(kăbə-shŏn′)
(kăbə-shŏn′)n.
1. A highly polished, convex-cut, unfaceted gem.
2. A convex style of cutting gems.
adv.
In a highly polished, convex-cut, unfaceted style: a sapphire that was cut cabochon.
[French, from Old North French, augmentative of caboche, head; see CABBAGE.]
cabochon