EPICYCLE
epicycle
(noun) a circle that rolls around (inside or outside) another circle; generates an epicycloid or hypocycloid
Source: WordNet® 3.1
Etymology
Noun
epicycle (plural epicycles)
(astronomy) A small circle whose centre is on the circumference of a larger circle; in Ptolemaic astronomy it was seen as the basis of revolution of the "seven planets", given a fixed central Earth.
(mathematics) Any circle whose circumference rolls around that of another circle, thus creating a hypocycloid or epicycloid.
(organic chemistry) A ring of atoms joining parts of an already cyclic compound
Source: Wiktionary
Ep"i*cy`cle, n. Etym: [L. epicyclus, Gr. Cycle.]
1. (Ptolemaic Astron.)
Definition: A circle, whose center moves round in the circumference of a
greater circle; or a small circle, whose center, being fixed in the
deferent of a planet, is carried along with the deferent, and yet, by
its own peculiar motion, carries the body of the planet fastened to
it round its proper center.
The schoolmen were like astronomers which did feign eccentries, and
epicycles, and such engines of orbs. Bacon.
2. (Mech.)
Definition: A circle which rolls on the circumference of another circle,
either externally or internally.
Source: Webster’s Unabridged Dictionary 1913 Edition