A line generated by a point on a circle rolling around another circle

Wiktionary Word definitions in Wiktionary
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.

WordNet Word definitions in WordNet
n. a line generated by a point on a circle rolling around another circle

Wikipedia Word definitions in Wikipedia
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 .

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
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, ...