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equa·tor
\ēˈkwād.ə(r), ə̇ˈk- also ˈēˌk-\ noun
(-s)
Etymology: Middle English, from Medieval Latin aequator, from Latin aequatus (past participle of aequare to make equal) + -or — more at equable
1. : the great circle of the celestial sphere whose plane is perpendicular to the axis of the earth : celestial equator
2. : the great circle midway between the poles of rotation of a planet, star, or other celestial body; specifically : a great circle of the earth that is everywhere equally distant from the two poles and divides the earth's surface into the northern and southern hemispheres and that is the line from which latitudes are reckoned, its own latitude being everywhere 0 degrees — see zone illustration
3. : a circle or circular band dividing the surface of a body into two usually equal and symmetrical parts
< the rainfall equator >
especially : a circle about a body at the place of its greatest width
< equator of a balloon >
< equator of an egg >
< equator of the eyeball >
4. : the circle on a surface of revolution that bisects its meridians; specifically : great circle |