Mathematics A three-dimensional surface, all points of which are equidistant from a fixed point, The sky, appearing as a hemisphere to an observer, An orbicular body representing the earth or the apparent heavens, or illustrating their astronomical relations, transitive verb_ To place in a sphere, or among the spheres; to insphere, To form into roundness; to make spherical, or spheral; to perfect, To make round or spherical; to perfect