Cycloid

n. [Fr. cycloïde, from Gr. κύκλος, circle, and εἶδος, form.] (Geom.) A curve generated by a point in the plane of a circle when the circle is rolled along a straight line, keeping always in the same plane.

☞ The common cycloid is the curve described when the generating point is on the circumference of the generating circle; the curtate cycloid, when that point lies without the circumference; the prolate or inflected cycloid, when the generating point lies within that circumference. Math. Dict.