cycle

n. 1 a recurrent round or period (of events, phenomena, etc.). B time needed for this. 2 a physics etc. Recurrent series of operations or states. B electr. = *hertz. 3 series of related songs, poems, etc. 4 bicycle, tricycle, etc. v. (-ling) 1 ride a bicycle etc. 2 move in cycles. [greek kuklos circle]

n. An imaginary circle or orbit in the heavens; one of the celestial spheres.