(ש"ע) נסיגה; ירידה

n. reversion to a previous condition; backward movement, retreat

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Noun
1. passing from a more complex to a simpler biological form
(synonym) degeneration
(hypernym) transformation, transmutation, shift
(hyponym) abiotrophy
2. returning to a former state
(synonym) regression, regress, reversion, retroversion
(hypernym) reversal
(derivation) regress, retrograde, retrogress

nf. retrogression, reversion to a previous condition

(n.)
The act of retrograding, or going backward; retrogradation.
  

(n.)
Backward development; a passing from a higher to a lower state of organization or structure, as when an animal, approaching maturity, becomes less highly organized than would be expected from its earlier stages or known relationship. Called also retrograde development, and regressive metamorphism.
  

(or Retrograde Motion) - Movement of a weather system in a direction opposite to that of the basic flow in which it is embedded, usually referring to a closed low or a longwave trough which moves westward.