Definition of "asterism"

Of the constellations, or asterisms. [...] It therefore became necessary to adopt a more general method of distinguishing them. This was accomplished by portioning out the heavens into imaginary figures, of men, birds, fishes, &c. called Constellations or Asterisms.

1825, Geo G. Carey, Astronomy, as it is known at the present day, London, p. 66 f

Like Pisces and Capricorn, Aquarius is located in that part of the sky known as "Astral Sea," a region inhabited by water asterisms such as Eridanus, Cetus (the Whale), and the Dolphin.

2007, Matilde Battistini, Rosanna M. Giammanco Frongia (translation from Italian into English), Astrology, Magic, and Alchemy in Art, page 60