Plan"i*sphere (?), n. [Plani- + sphere: cf. F. planisphere. See Plain, and Sphere.]
The representation of the circles of the sphere upon a plane; especially, a representation of the celestial sphere upon a plane with adjustable circles, or other appendages, for showing the position of the heavens, the time of rising and setting of stars, etc., for any given date or hour.
© Webster 1913.