Dictionary.net

• A curve, traced by a point in the radius, or radius produced, of a circle which rolls upon the concave side of a fixed circle. See Hypocycloid, Epicycloid, and Trochoid.

2010 - New Age Dictionary Database
By Oddity Software

• A curve, traced by a point in the radius, or radius produced, of a circle which rolls upon the concave side of a fixed circle. See Hypocycloid, Epicycloid, and Trochoid.

1913 - Webster's Revised Unabridged Dictionary
By Noah Webster.