See zodiac in Webster's New World College Dictionary
noun
a beltlike zone in the sky extending for about eight degrees on either side of the apparent path of the sun and including the paths of the moon and the principal planets: it is divided into twelve equal parts, or signs, each named for a different constellation
a figure or diagram representing the zodiac and its signs: used in astrology
a. Astronomy A band of the celestial sphere extending about 8° to either side of the ecliptic that represents the path of the principal planets, the moon, and the sun.
b. In astrology, this band divided into 12 equal parts called signs, each 30° wide, bearing the name of a constellation for which it was originally named but with which it no longer coincides owing to the precession of the equinoxes.