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apsidal motion

American

noun

Astronomy.

the rotation of the major axis of an eccentric orbit in the plane of the orbit.

Etymology

Origin of apsidal motion

First recorded in 1955–60

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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.