SG Heritage Dictionary

Evolute [Noun] Webster's Dictionary 1828

An original curve from which another curve is described; the origin of the evolent.

Evolute [Noun] Webster's Dictionary 1913

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.