What is Epicycle?

Epicycle definition and meaning on Dictionary terms:
Astronomy. 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.
Mathematics. a circle that rolls, externally or internally, without slipping, on another circle, generating an epicycloid or hypocycloid.


reference: https://www.dictionary.com/browse/epicycle