(a) Astron. The elliptical path followed by the center of a planet's epicycle as it appears to move about the earth; also, a representation of such an orbit on the instrument called an equatorie; (b) as adj.: centre ~, the moving center of the defferent of a planet; also, a hole representing such a center on an instrument; cercle ~, a circle described by the motion of a centre defferent; also, a representation of such a circle; commune centre ~, a hole, in the limb of the epicycle part of an equatorie, which serves as centre defferent for all of the planets [see fig. 12 in Price & Wilson, EPlanets p.102].