Sagitta \Sa*git"ta\, n. [L., an arrow.]

1. (Astron.) A small constellation north of Aquila; the Arrow.

2. (Arch.) The keystone of an arch. [R.]

--Gwilt.

3. (Geom.) 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. [Obs.]

4. (Anat.) The larger of the two otoliths, or ear bones, found in most fishes.

5. (Zo["o]l.) 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 Ch[ae]tognatha.

Source: Webster's Revised Unabridged Dictionary (1913)