armillary sphere: Meaning and Definition of

ar'millary sphere'

Pronunciation: [key]
— Astron. Astron.
  1. an ancient instrument consisting of an arrangement of rings, all of which are circles of the same sphere, used to show the relative positions of the celestial equator, ecliptic, and other circles on the celestial sphere.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.