either of two great circles of the celestial sphere intersecting each other at the poles, one passing through both equinoxes and the other through both solstices.
Origin: 1540–50; < Late Latin colūrus < Greek kólouros dock-tailed, equivalent to kól(os) docked + -ouros -tailed, adj. derivative of ourá tail; so called because the lower part is permanently hidden beneath the horizon
either of two great circles on the celestial sphere, one of which passes through the celestial poles and the equinoxes and the other through the poles and the solstices
[C16: from Late Latin colūrī (plural), from Greek kolourai cut short, dock-tailed, from kolos docked + oura tail; so called because the view of the lower part is curtailed]