WordNet (r) 3.0 (2006):

picture element
    n 1: (computer science) the smallest discrete component of an
         image or picture on a CRT screen (usually a colored dot);
         "the greater the number of pixels per inch the greater the
         resolution" [syn: pixel, pel, picture element]

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

picture element
pixel

    (pixel) The smallest resolvable rectangular area of
   an image, either on a screen or stored in memory.  Each
   pixel in a monochrome image has its own brightness, from 0
   for black to the maximum value (e.g. 255 for an eight-bit
   pixel) for white.  In a colour image, each pixel has its own
   brightness and colour, usually represented as a triple of red,
   green and blue intensities (see RGB).

   Compare voxel.

   (1998-05-08)