1. In Ptolemaic cosmology, a small circle, the center of which moves on the circumference of a larger circle at whose center is the earth and the circumference of which describes the orbit of one of the planets around the earth.
2. Mathematics A circle whose circumference rolls along the circumference of a fixed circle, thereby generating an epicycloid or a hypocycloid.
[Middle English epicicle, from Late Latin epicyclus, from Greek epikuklos : epi-, epi- + kuklos, circle; see kwel-1 in the Appendix of Indo-European roots.]
ep′i·cyclic (-sĭklĭk, -sīklĭk) adj.
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