demilune

Etymology
Borrowed from.

Adjective

 * 1)  In the shape of a half-moon, i.e. semicircular.

Noun

 * 1)  A fortification constructed beyond the main ditch of a fortress, and in front of the curtain between two bastions, intended to defend the curtain; a ravelin.
 * 2)  A crescentic mass of granular protoplasm present in the salivary glands.