[equa.tor] n [ME, fr. ML aequator, lit., equalizer, fr. L aequare] (14c) 1: the great circle of the celestial sphere whose plane is perpendicular to the axis of the earth
2: a great circle of the earth or a celestial body that is everywhere equally distant from the two poles and divides the surface into the northern and southern hemispheres 3 a: a circle or circular band dividing the surface of a body into two usu. equal and symmetrical parts b: equatorial plane "the ~ of a dividing cell"
4: great circle