involution

noun9

1. •
   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. — 1938
2. •
   A complicated grammatical construction.

   • Walter Pater’s essay on Style is honeycombed with involutions and preciosity. — 1917
3. •
   A cessation of development or progress involving intense inner competition.
4. •
   A state of increased competition for limited resources, requiring great effort to stay ahead.
5. •
   The shrinking of an organ (such as the uterus) to a former size.
6. •
   The regressive changes in the body occurring with old age.
7. •
   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. — 1996
8. •
   The migration of a cell layer inward, sliding over an outer layer of cells. It occurs at gastrulation during embryogenesis.
9. •
   (no longer used) A power: the result of raising one number to the power of another.