ˈepəˌsīkəl noun
Etymology: Middle English epicicle, from Late Latin epicyclus, from Greek epikyklos, from epi- + kyklos ring circle, cycle, wheel — more at wheel
1.
a. in Ptolemaic astronomy : a circle in which a planet moves and which has a center that is itself carried around at the same time on the circumference of a larger circle
b. : a process of activity going on within the context of a larger one : secondary cycle
an epicycle of land erosion
2. : the circle generating an epicycloid or hypocycloid