Pronunciation: (lOO-net'),[key] —n. 1. any of various objects or spaces of crescentlike or semicircular outline or section.
2. Archit.(in the plane of a wall) an area enframed by an arch or vault.
3. a painting, sculpture, or window filling such an area.
4. Fort.a work consisting of a salient angle with two flanks and an open gorge.
5. Ordn.a towing ring in the trail plate of a towed vehicle, as a gun carriage.
6. Eccles.Luna (def. 3).