demilune
/ˈdemɪljuːn/noun
1- a crescent or half-circle, or a thing of this shape新月, 半月; 半月形; 半月形物。
1.1
- (in a fortified building) an outwork resembling a bastion, with a crescent-shaped gorge半月形工事, 半月堡。
词源
early 18th cent.: from French demi-lune, literally 'half-moon'.