Sagitta
Sagitta , noun
[Latin, an arrow.]
1.
(Astronomy) A small constellation north of Aquila; the Arrow.
2.
(Architecture) The keystone of an arch. [Rare] — Gwilt
3.
(Geometry) The distance from a point in a curve to the chord; also, the versed sine of an arc; -- so called from its resemblance to an arrow resting on the bow and string. [Obsolete]
4.
(Anatomy) The larger of the two otoliths, or ear bones, found in most fishes.
5.
(Zoology) A genus of transparent, free-swimming marine worms having lateral and caudal fins, and capable of swimming rapidly. It is the type of the class Chaetognatha.