Definition of "precession" [pre•ces•sion]

• The act or state of preceding; precedence. (noun)
• Physics The motion of the axis of a spinning body, such as the wobble of a spinning top, when there is an external force acting on the axis. (noun)
• Astronomy Precession of the equinoxes. (noun)
• Astronomy A slow gyration of the earth's axis around the pole of the ecliptic, caused mainly by the gravitational pull of the sun, moon, and other planets on the earth's equatorial bulge. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "(The observed precession is really 5270 ''/century, but a painstaking calculation to subtract the disturbances from all the other planets gives the value of 43 ''.)"
• "Kunkle's re-examining of astrology is rooted in the Earth's "precession" -- put simply, the gravity-fueled change in orientation of the Earth's rotational axis."
• "Another aspect of the precession is the length of winter and summer."