WordNet (r) 3.0 (2006):

bitmap
    n 1: an image represented as a two dimensional array of
         brightness values for pixels [syn: bitmap, electronic
         image]

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

bitmap

    A data file or structure which
   corresponds bit for bit with an image displayed on a
   screen, probably in the same format as it would be stored in
   the display's video memory or maybe as a device independent
   bitmap.  A bitmap is characterised by the width and height of
   the image in pixels and the number of bits per pixel which
   determines the number of shades of grey or colours it can
   represent.  A bitmap representing a coloured image (a
   "pixmap") will usually have pixels with between one and
   eight bits for each of the red, green, and blue components,
   though other colour encodings are also used.  The green
   component sometimes has more bits that the other two to cater
   for the human eye's greater discrimination in this component.

   See also vector graphics, image formats.

   (1996-09-21)