Main Entry: in·vo·lu·tion

Pronunciation: \ˌin-və-ˈlü-shən\

Function: noun

Etymology: Latin involution-, involutio, from involvere

Date: circa 1611

1 a (1) : the act or an instance of enfolding or entangling : involvement (2) : an involved grammatical construction usually characterized by the insertion of clauses between the subject and predicate b : complexity, intricacy
2 : exponentiation
3 a : an inward curvature or penetration b : the formation of a gastrula by ingrowth of cells formed at the dorsal lip
4 : a shrinking or return to a former size
5 : the regressive alterations of a body or its parts characteristic of the aging process <skeletal involution due to loss of estrogens at menopause>

— in·vo·lu·tion·al \-shnəl, -shə-n^əl\ adjective