Source : WordNet®

halftone
     n 1: a print obtained from photoengraving
     2: an engraving used to reproduce an illustration [syn: {halftone
        engraving}, {photoengraving}]

Source : Free On-Line Dictionary of Computing

halftone
     
         The reproducion of {greyscale} {images} using dots
        of a single shade but varying size to simulate the different
        shades of grey.
     
        {Laser printers} that cannot print different sized dots,
        halftones are produced by varying the numbers of dots in a
        given area.
     
        This process is also used to produce a black and white version
        of a colour original using shades of grey in place of colours.
     
        See also {device independent bitmap}.
     
        (1996-09-20)