Sagitta

1. n. 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.
2. n. A small constellation north of Aquila; the Arrow.
3. n. The keystone of an arch.
4. n. 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.
5. n. The larger of the two otoliths, or ear bones, found in most fishes.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.