Definition of "equator"

(geography, often “the Equator”) An imaginary great circle around Earth, equidistant from the two poles, and dividing earth's surface into the northern and southern hemisphere.  quotations  examples

(astronomy) A similar great circle on any sphere, especially on a celestial body, or on other reasonably symmetrical three-dimensional body.  examples

The midline of any generally spherical object, such as a fruit or vegetable, that has identifiable poles.  examples

The celestial equator.  examples