Epicycle

ep′i-sī-kl, n. a circle having its centre on the circumference of a greater circle on which it moves.— adj. Epicy′clic .— n. Epicy′cloid , a curve described by every point in the plane of a circle moving on the convex circumference of another circle.— adj. Epicycloi′dal . [Gr. epi , upon, kyklos , a circle.]