Answer: involution

AnswerCrossword Clue
involutionA function, transformation, or operator that is equal to its inverse, i.e., which gives the identity when applied to itself
involutionThe shrinkage of an organ in old age or when inactive, e.g., of the uterus after childbirth
involutionThe process of involving or complicating, or the state of being involved or complicated
involutionthe act of involving or infolding