Definition of: involute

(in′və·lt) adjective
1. Complicated by reason of the intertwinings or the interrelation of parts or elements.
2. Bot. Having the edges rolled inward, as a leaf.
3. Zool. Having the whorls nearly or quite concealing the axis, as a shell; also, coiled spirally, as certain antennae. Also in′vo·lut′ed.
—noun Geom. The curve traced by a point on a line as the line unrolls from a fixed curve. [<L involutus, pp. of involvere involve]
INVOLUTE
Involute AC is formed by the locus of point P (at P¹, P², P³, P⁴) as line BC unrolls from curve BA. Length of the tangent to the curve (P¹ Q¹, P² Q², etc.) from any point on the involute AC is equal to the length of the curve to the point of tangency (AQ¹ = P¹Q¹; AQ² = P²Q²; etc.).