WordNet (r) 3.0 (2006):

dithering
    n 1: the process of representing intermediate colors by patterns
         of tiny colored dots that simulate the desired color

The Free On-line Dictionary of Computing (30 December 2018):

dithering

    A technique used in quantisation processes
   such as graphics and audio to reduce or remove the
   correlation between noise and signal.

   Dithering is used in computer graphics to create additional
   colors and shades from an existing palette by interspersing
   pixels of different colours.  On a monochrome display,
   areas of grey are created by varying the proportion of black
   and white pixels.  In colour displays and printers, colours
   and textures are created by varying the proportions of
   existing colours.  The different colours can either be
   distributed randomly or regularly.  The higher the
   resolution of the display, the smoother the dithered colour
   will appear to the eye.

   Dithering doesn't reduce resolution.  There are three types:
   regular dithering which uses a very regular predefined
   pattern; random dither where the pattern is a random noise;
   and pseudo random dither which uses a very large, very
   regular, predefined pattern.

   Dithering is used to create patterns for use as backgrounds,
   fills and shading, as well as for creating halftones for
   printing.  When used for printing is it very sensitive to
   paper properties.  Dithering can be combined with
   rasterising.  It is not related to anti-aliasing.

   (2003-07-20)