Straight and flat across, parallel to the horizon. The opposite is vertical. All other directions are diagonal.Examples of notably horizontal works: Maurits Cornelis Escher (Dutch , 1898-1972), Metamorphosis II. See metamorphosis, Op Art, optical illusion, and tessellation. see thumbnail above Kenneth Snelson (American, 1927-), Brooklyn Bridge, 1980, gelatin silver print, 15 1/2 x 91 5/15 inches, Cleveland Museum of Art. See panorama and photography. In graphics software, to make the following change is to "flip horizontally"a dog facing to the leftis flipped horizontally when it is seen asa dog facing to the rightAlso see align and alignment, frieze, horizon line, invert, and perpendicular.