1. (n.) An orthographic projection of the sphere on the plane of the meridian, the eye being supposed at an infinite distance, and in the east or west point of the horizon.

2. (n.) An instrument of wood or brass, on which this projection of the sphere is made, having a movable horizon or cursor; -- formerly much used in solving some common astronomical problems.

3. (n.) A scale of the sun's declination for each day of the year, drawn across the torrid zone on an artificial terrestrial globe.