An asterism is a small grouping of stars that does not make up one of the 88 complete constellations recognized by the International Astronomical Union. Asterisms often make use of bright stars in several constellations (such as the Summer Triangle), or they may be parts of a constellation that are described in terms of more well-known objects (for example, the Big Dipper of Ursa Major, the saucepan of Orion’s belt, or the teapot of Sagittarius). The stars in an asterism generally have no physical association, and are located at vastly different distances from the Solar System. Two notable exceptions are the Hyades and the Pleaides, both of which are open star clusters in the constellation Taurus.

left: The stars of the complete constellation Orion.
middle: Orion the Hunter.
right: Orion the saucepan.
Both the hunter and the saucepan are asterisms

left: The stars of the complete constellation Sagittarius.
right: Sagittarius the teapot is an asterism.