\Ev"o*lute\, n. [L. evolutus unrolled, p. p. of
evolvere. See {Evolve}.] (Geom.)
A curve from which another curve, called the involute or
evolvent, is described by the end of a thread gradually wound
upon the former, or unwound from it. See {Involute}. It is
the locus of the centers of all the circles which are
osculatory to the given curve or evolvent.
Note: Any curve may be an evolute, the term being applied to
      it only in its relation to the involute.