An imaginary great circle around the earth, equidistant from the two poles, and dividing earth's surface into the northern and southern hemisphere.
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"
a circle dividing a sphere or other surface into two usually equal and symmetrical parts
an imaginary line around the Earth forming the great circle that is equidistant from the north and south poles