Sphĕr'o-grāph, n.

n. [Gr. σφαῖρα, sphere, and γράφειν, to write, describe.] An instrument for facilitating the practical use of spheres in navigation and astronomy, being constructed of two card-boards containing various circles, and turning upon each other in such a manner that any possible spherical triangle may be readily found, and the measures of the parts read off by inspection.