(astronomy) A small circle whose centre is on the circumference of a larger circle; in Ptolemaic astronomy it was seen as the basis of revolution of the "seven planets", given a fixed central Earth.

plural of epicycle

Of or relating to epicycles. / Of a gearbox, having two gears mounted so that the center of one gear revolves around the center of the other.

Of or pertaining to an epicycle.

a system of gears that has a central gear wheel around which others rotate, often within an outer ring

plural of epicyclic gear