— epicyclic /ep'euh suy"klik, -sik"lik/ , adj.
/ep"euh suy'keuhl/ , n.
1. Astron. a small circle the center of which moves around in the circumference of a larger circle: used in Ptolemaic astronomy to account for observed periodic irregularities in planetary motions.
2. Math. a circle that rolls, externally or internally, without slipping, on another circle, generating an epicycloid or hypocycloid.
[ 1350-1400; ME epicyclus epíkyklos. See EPI-, CYCLE ]