equator Meaning, Definition & Usage

  1. noun 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
  2. noun a circle dividing a sphere or other surface into two usually equal and symmetrical parts

WordNet

E*qua"tor noun
Etymology
L. aequator one who equalizes: cf. F. équateur equator. See Equate.
Definitions
  1. (Geog.) 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.
  2. (Astron.) 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.

Webster 1913