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Found one definition

1.                 From The Free On-line Dictionary of Computing (19 January 2023):
                   
   
   
                   
                     
   lossless
      <algorithm, compression> A term describing a data
      compression algorithm which retains all the information in
      the data, allowing it to be recovered perfectly by
      decompression.
      Unix compress and GNU gzip perform lossless
      compression.
      Opposite: lossy.
      (1995-03-29)