(Geometry)a small circle whose centre moves round the circumference of a larger one (几何)周转圆 ■(historical)a circle of this type used to describe planetary orbits in the Ptolemaic system (史)本轮
派生 epicyclic adjective 语源
late Middle English: from Old French, or via late Latin from Greek epikuklos, from epi 'upon' + kuklos 'circle'