Epicycle

·noun A circle which rolls on the circumference of another circle, either externally or internally.

II. Epicycle ·noun A circle, whose center moves round in the circumference of a greater circle; or a small circle, whose center, being fixed in the deferent of a planet, is carried along with the deferent, and yet, by its own peculiar motion, carries the body of the planet fastened to it round its proper center.