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. [1913 Webster]
"The schoolmen were like astronomers which did feign eccentrics, and epicycles, and such engines of orbs." [1913 Webster]
A circle which rolls on the circumference of another circle, either externally or internally. [1913 Webster]

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OXFORD DICTIONARY

epicycle, n. Geom. a small circle moving round the circumference of a larger one.

Derivative

epicyclic adj.

Etymology

ME f. OF or LL epicyclus f. Gk epikuklos (as EPI-, kuklos circle)

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ROGET THESAURUS

epicycle

Circularity

N circularity, roundness, rotundity, circle, circlet, ring, areola, hoop, roundlet, annulus, annulet, bracelet, armlet, ringlet, eye, loop, wheel, cycle, orb, orbit, rundle, zone, belt, cordon, band, contrate wheel, crown wheel, hub, nave, sash, girdle, cestus, cincture, baldric, fillet, fascia, wreath, garland, crown, corona, coronet, chaplet, snood, necklace, collar, noose, lasso, lassoo, ellipse, oval, ovule, ellipsoid, cycloid, epicycloid, epicycle, semicircle, quadrant, sextant, sector, sphere, round, rounded, circular, annular, orbicular, oval, ovate, elliptic, elliptical, egg-shaped, pear-shaped, cycloidal, spherical, I watched the little circles die.

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