epicycle

noun

epi·​cy·​cle ˈe-pə-ˌsī-kəl 

1

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

2

: a process going on within a larger one

epicyclic

ˌe-pə-ˈsī-klik 

-ˈsi-klik

adjective

Examples of epicycle in a Sentence

Recent Examples on the Web

The Ptolemaic model depicted planets moving around Earth in a big circle, known as a deferent, then going around a smaller circle while retrograding, called an epicycle. —Carlie Procell, USA TODAY, 25 Nov. 2024

Amid these complications, Tomas proves to be a spontaneous provocateur, producing further epicycles of enmity and turmoil. —Richard Brody, The New Yorker, 8 Aug. 2023

In order to reconcile circular orbits with actual planetary behavior, Copernicus continued the tradition, developed by Ptolemy, of arguing that planets spin on wheels, known as epicycles. —National Geographic, 9 Apr. 2019

Word History

Etymology

Middle English epicicle, from Late Latin epicyclus, from Greek epikyklos, from epi- + kyklos circle — more at wheel

First Known Use

14th century, in the meaning defined at sense 1

Kids Definition

epicycle

noun

epi·​cy·​cle ˈep-ə-ˌsī-kəl 

: a circle according to an early astronomy theory 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