What is "lunette window"

Lunette \Lu*nette"\, n. [F., dim. of lune moon, L. luna. See Lune a crescent.]

1. (Fort.) A fieldwork consisting of two faces, forming a salient angle, and two parallel flanks. See Bastion.

2. (Far.) A half horseshoe, which lacks the sponge.

3. A kind of watch crystal which is more than ordinarily flattened in the center; also, a species of convexoconcave lens for spectacles.

4. A piece of felt to cover the eye of a vicious horse.

5. (Arch.) Any surface of semicircular or segmental form; especially, the piece of wall between the curves of a vault and its springing line.

6. An iron shoe at the end of the stock of a gun carriage.

   Lunette window (Arch.), a window which fills or partly fills a lunette.