Medical Definition of involution
1a: an inward curvature or penetrationb: the formation of a gastrula by ingrowth of cells formed at the dorsal lip
2: a shrinking or return to a former size <involution of the uterus after pregnancy>
3: the regressive alterations of a body or its parts characteristic of the aging process; specifically : decline marked by a decrease of bodily vigor and in women by menopause
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