ˌ ̷ ̷ ̷ ̷ˈgreshən noun
( -s )
Etymology: Latin retrogress us (past participle) + English -ion
1. : regression 3
2. : a reversal in development or condition: as
a. : a passing from a higher to a lower or from a more to a less specialized state or type of organization or structure in the course of the development of an organism
b. : subsidence or decline of symptoms or manifestations of a disease
c. : retrograde imitation in contrapuntal music