<p><strong>Noun</strong></p><ul><li>The great circle on a sphere or heavenly body whose plane is perpendicular to the axis, equidistant everywhere from the two poles of the sphere or heavenly body.</li><li>The great circle of the earth that is equidistant from the North Pole and South Pole.</li><li>A circle separating a surface into two congruent parts.</li><li>Celestial equator.</li></ul>