The Collaborative International Dictionary of English v.0.48:

Compression \Com*pres"sion\, n. [L. compressio: cf. F.
   compression.]
   1. The act of compressing, or state of being compressed.
      "Compression of thought." --Johnson.
      [1913 Webster]

   2. (Computers) reduction of the space required for storage
      (of binary data) by an algorithm which converts the data
      to a smaller number of bits while preserving the
      information content. The act of compressing [3].

   Note: Compression may be lossless compression, in which all
         of the information in the original data is preserved,
         and the original data may be recovered in form
         identical to its original form; or lossy compression,
         in which some of the information in the original data
         is lost, and decompression results in a data form
         slightly different from the original. Lossy
         compression is used, for example, to compress audio or
         video recordings, and sometimes images, where the
         slight differences in the original data and the data
         recovered after lossy compression may be
         imperceptable to the human eye or ear. The JPEG
         format is produced by a lossy compression algorithm.
         [PJC]

The Collaborative International Dictionary of English v.0.48:

JPEG \JPEG\ n. [Acronym from Joint Picture Experts Group.]
   (Computers)
   A standardized format for storing graphic data in binary
   computer files, allowing over 16 million different colors. It
   allows for lossy compression, i. e. the compression of data
   into a form which re-expands into an image close, but not
   identical to the original image. Files stored in this format
   usually carry the extension jpg or jpeg. Compare GIF.
   [PJC]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

JPEG
       Joint Photographics Expert Group (org., JTC1, RFC 1521, JPEG)


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

Joint Photographic Experts Group
JPEG
jpg

    (JPEG) The original name
   of the committee that designed the standard image
   compression algorithm.  JPEG is designed for compressing
   either full-colour or grey-scale digital images of
   "natural", real-world scenes.  It does not work so well on
   non-realistic images, such as cartoons or line drawings.  JPEG
   does not handle compression of black-and-white (1
   bit-per-pixel) images or moving pictures.  Standards for
   compressing those types of images are being worked on by other
   committees, named JBIG and MPEG.

   (http://jpeg.org/).

   Filename extension: .jpg, .jpeg.

   See also PJPEG.

   (2000-09-11)