\In`vo*lu"tion\, n. [L. involutio: cf. F. involution.
See {Involve}.]
1. The act of involving or infolding.
2. The state of being entangled or involved; complication;
   entanglement.
         All things are mixed, and causes blended, by mutual
         involutions.                          --Glanvill.
3. That in which anything is involved, folded, or wrapped;
   envelope. --Sir T. Browne.
4. (Gram.) The insertion of one or more clauses between the
   subject and the verb, in a way that involves or
   complicates the construction.
5. (Math.) The act or process of raising a quantity to any
   power assigned; the multiplication of a quantity into
   itself a given number of times; -- the reverse of
   evolution.
6. (Geom.) The relation which exists between three or more
   sets of points, a.a', b.b', c.c', so related to a point O
   on the line, that the product Oa.Oa' = Ob.Ob' = Oc.Oc' is
   constant. Sets of lines or surfaces possessing
   corresponding properties may be in involution.
7. (Med.) The return of an enlarged part or organ to its
   normal size, as of the uterus after pregnancy.