n. 1. a. The act of involving. b. The state of being involved. 2. Intricacy; complexity. 3. Something, such as a long grammatical construction, that is intricate or complex. 4. Mathematics An operation, such as negation, which, when applied to itself, returns the original number. 5. Embryology The ingrowth and curling inward of a group of cells, as in the formation of a gastrula from a blastula. 6. Medicine a. A decrease in size of an organ, as of the uterus following childbirth. b. A progressive decline or degeneration of normal physiological functioning occurring as a result of the aging process. [Latin involūtiō, involūtiōn-, from involūtus, past participle of involvere, to enwrap; see INVOLVE.] in′vo·lution·al adj. |
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