Definition of: equator

(i·kwā′tər) noun
1. A great circle of the earth, a planet, etc., lying at right angles to its axis and equidistant from the poles.
2. Any similar circle, as of the sun, a planet, etc.
3. The celestial equator. [<LL (circulus) aequator equalizer (circle); so called because day and night are equal when the sun crosses the equator]
EQUATOR
e. Equator.
noun North pole.
s. South pole.