1. 1. 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.
   2. 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.
   3. A diagram or figure representing the zodiac.
2. A complete circuit; a circle.

[Middle English, from Old French zodiaque, from Latin zōdiacus, from Greek zōidiakos (kuklos), (circle) of the zodiac, from zōidion, small represented figure, zodiacal sign, diminutive of zōion, living being. See zoon¹.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.