- 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. - The great circle of the celestial sphere, coincident with
the plane of the earth's equator; -- so called because when the sun is
in it, the days and nights are of equal length; hence called also the
equinoctial, and on maps, globes, etc., the equinoctial line.
Meaning of 'equator' (Princeton's WordNet)
1 . equator
[ n]
Meaning (1): - an imaginary line around the Earth forming the great circle that is equidistant from the north and south poles
Example in sentence:
the equator is the boundary between the northern and southern hemispheres