WordNet sense 1 (having a surface free from roughness or bumps or ridges or irregularities):

smooth

WordNet sense 2 ((of ceramics) having the surface made shiny and nonporous by fusing a vitreous solution to it):

vitreous, vitrified

WordNet sense 3 (having a shiny surface or coating):

glazed, shiny

WordNet sense 4 (holding or containing nothing):

empty