Hypocycloid
Pronunciation : Hy`po*cy"cloid
Part of Speech : n.
Etymology : [Pref. hypo- + cycloid: cf. F. hypocyclo?de.] (Geom.)
Definition : Defn: A curve traced by a point in the circumference of a circle which rolls on the concave side in the fixed circle. Cf. Epicycloid, and Trochoid.
Source : Webster's Unabridged Dictionary, 1913