Sagitta

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A constellation in the Northern Hemisphere near Aquila and Vulpecula.

from The Century Dictionary.

• noun [capitalized] An insignificant but very ancient northern constellation, the Arrow, placed between Aquila and the bill of the Swan.
• noun In anatomy, the sagittal suture.
• noun In ichthyology, one of the otoliths of a fish's ear.
• noun [capitalized] The typical genus of Sagittidæ, formerly containing all the species, now restricted to those with two pairs of lateral fins besides the caudal fin. Also Saggitta, Saggita, Sagita. See accompanying cut.
• noun An arrow-worm or sea-arrow; a member of the Sagittidæ.
• noun The keystone of an arch.
• noun In geometry: The versed sine of an arc: so called by Kepler because it makes a figure like an arrow upon a bow.
• noun The abscissa of a curve.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Astron.) A small constellation north of Aquila; the Arrow.
• noun (Arch.), rare The keystone of an arch.
• noun (Geom.), obsolete 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.
• noun (Anat.) The larger of the two otoliths, or ear bones, found in most fishes.
• noun (Zoöl.) 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 Chætognatha.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• proper noun astronomy A small autumn constellation of the northern sky, said to resemble an arrow. It lies between the constellations of Vulpecula and Aquila.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a small constellation in the northern hemisphere between Cygnus and Aquila and crossed by the Milky Way
• noun any arrowworm of the genus Sagitta