[ lu:'nɛt ]
■ noun
1》 an arched aperture or window in a domed ceiling.
↘a crescent-shaped or semicircular alcove containing a painting or statue.
2》 a fortification with two faces forming a projecting angle, and two flanks.
3》 Christian Church a holder for the consecrated host in a monstrance.
4》 a ring on a vehicle, by which it can be towed.
Origin
C16 (denoting a semicircular horseshoe): from Fr., dimin. of lune 'moon', from L. luna .