retrogression

[ re-truh-gresh-uh n ]
/ ˌrɛ trəˈgrɛʃ ən /

noun

the act of retrogressing; movement backward.
Biology. degeneration; retrograde metamorphosis; passing from a more complex to a simpler structure.

Origin of retrogression

1640–50; < Latin retrōgress(us) (see retrogress) + -ion
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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Medicine definitions for retrogression

retrogression
[ rĕt′rə-grĕshən ]

n.

The act or process of deteriorating or declining.
A return to a less complex biological state or stage.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.