encirclement
enclosing, skirting
An imaginary great circle around Earth, equidistant from the two poles, and dividing earth's surface into the northern and southern hemisphere.
The midline of any generally spherical object, such as a fruit or vegetable, that has identifiable poles.
A similar great circle on any sphere, especially on a celestial body, or on other reasonably symmetrical three-dimensional body.
The celestial equator.