involution

Entanglement; a spiralling inwards; intricacy.

[…]usually his attention was diverted from her feet by her shrieks of laughter and the astounding involutions of her huge brown-yellow frame.

‘Gomez,’ said the mortician, ‘is an expert only on the involutions of his own rectum.’

A complicated grammatical construction.

1917, James Huneker, Unicorns, New York: Scribner, Chapter 11 “Style and Rhythm in English Prose,” p. 129, Walter Pater’s essay on Style is honeycombed with involutions and preciosity.

An endofunction whose square is equal to the identity function; a function equal to its inverse.

Involutions have the property that they are their own inverses.

The shrinking of an organ (such as the uterus) to a former size.

The regressive changes in the body occurring with old age.