an imaginary circle that is drawn around the Earth such that it is equally distant from the North- and South poles, thus dividing the surface into two equal hemispheres;
e.g. Regions near the equator often have hot and humid climate.
(noun)
broadly, an imaginary line drawn around some body, especially a celestial body like a planet, so as to be located at equal distances from the two poles, thus dividing the surface into two hemispheres;
e.g. The cell divides along its equator to give rise to two identical daughter cells.