equator Definition

equator
noun

1. geog.
The imaginary great circle that passes around the Earth at latitude 0 at an equal distance from the North and South Poles, and divides the Earth's surface into the northern and southern hemispheres.
Form: the Equator (often)
2. astron.
The celestial equator.
3. A circle dividing a spherical body into two equal parts.

Etymology: 14c: from Latin aequator equalizer (of day and night).