involution

noun

1. reduction in size of an organ or part (as in the return of the uterus to normal size after childbirth)
2. a long and intricate and complicated grammatical construction
3. marked by elaborately complex detail
4. the act of sharing in the activities of a group"the teacher tried to increase his students' engagement in class activities"
5. the process of raising a quantity to some assigned power
6. the action of enfolding something