zo·di·ac (z??d?-?k?)n.1. 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.c. A diagram or figure representing the zodiac.2. A complete circuit; a circle.[Middle English, from Old French zodiaque, from Latin z?diacus, from Greek z?idiakos (kuklos), (circle) of the zodiac, from z?idion, small represented figure, zodiacal sign, diminutive of z?ion, living being; see zoon.]zo·di?a·cal (-d???-k?l) adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.zodiac (?z??d??æk) n1. (Astrology) an imaginary belt extending 8° either side of the ecliptic, which contains the 12 zodiacal constellations and within which the moon and planets appear to move. It is divided into 12 equal areas, called signs of the zodiac, each named after the constellation which once lay in it. See zodiacal constellation2. (Astrology) astrology a diagram, usually circular, representing this belt and showing the symbols, illustrations, etc, associated with each of the 12 signs of the zodiac, used to predict the future3. rare a complete circuit; circle[C14: from Old French zodiaque, from Latin z?diacus, from Greek z?idiakos (kuklos) (circle) of signs, from z?idion animal sign, carved figure, from z?ion animal] zodiacal adjCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014zo?di?ac (?zo? di?æk) n. 1. an imaginary belt extending about 8° on each side of the ecliptic and containing the paths of the sun, moon, and principal planets through 12 constellations or signs. 2. a diagram representing this and often containing the symbol for each sign of the zodiac. 3. a circuit or round. [1350?1400; Middle English zodiaque