an imaginary line around the Earth forming the great circle that is equidistant from the north and south poles
The equator is the boundary between the northern and southern hemispheres.
source: WordNet 3.0
a circle dividing a sphere or other surface into two usually equal and symmetrical parts
source: WordNet 3.0
The imaginary great circle on the earth's surface, everywhere equally distant from the two poles, and dividing the earth's surface into two hemispheres.
