The Collaborative International Dictionary of English v.0.48:

Involute \In"vo*lute\, n. (Geom.)
   A curve traced by the end of a string wound upon another
   curve, or unwound from it; -- called also evolvent. See
   Evolute.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Evolvent \E*volv"ent\, n. [L. evolvens, -entis, unrolling, p.
   pr. of evolvere.] (Geom.)
   The involute of a curve. See Involute, and Evolute.
   [1913 Webster]