[i-kwey-ter] 
| 1. | 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. |
| 2. | the great circle of the earth that is equidistant from the North Pole and South Pole. |
| 3. | a circle separating a surface into two congruent parts. |
| 4. | celestial equator. |
| the great circle of the celestial sphere, lying in the same plane as the earth's equator. |
e·qua·tor (ĭ-kwā'tər)  (click for larger image in new window) n.
[Middle English, from Medieval Latin aequātor (diēī et noctis), equalizer (of day and night), from Latin aequāre, to equalize; see equate.] |
An imaginary circle around the Earth, equidistant from the North Pole and South Pole.
tər
