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; < LL colūrus < Gk kólouros dock-tailed, equiv. to kól(os) docked + -ouros -tailed, adj. deriv. of ourá tail; so called because the lower part is permanently hidden beneath the horizon
[kuh-loo
r, koh-, koh-loo