What is "epicycloid"

Epicycloid \Ep`i*cy"cloid\, n. [Epicycle + -oid: cf. F. ['e]picyclo["i]de.] (Geom.) A curve traced by a point in the circumference of a circle which rolls on the convex side of a fixed circle.

Note: Any point rigidly connected with the rolling circle, but not in its circumference, traces a curve called an epitrochoid. The curve traced by a point in the circumference of the rolling circle when it rolls on the concave side of a fixed circle is called a hypocycloid; the curve traced by a point rigidly connected with the rolling circle in this case, but not its circumference, is called a hypotrochoid. All the curves mentioned above belong to the class class called roulettes or trochoids. See Trochoid.

n. (context geometry English) The locus of a point on the circumference of a circle that rolls without slipping on the circumference of another circle.

n. a line generated by a point on a circle rolling around another circle

In geometry, an epicycloid is a plane curve produced by tracing the path of a chosen point on the circumference of a circle — called an epicycle — which rolls without slipping around a fixed circle. It is a particular kind of roulette.