Source : WordNet®

REM
     n 1: a recurring sleep state during which dreaming occurs; a
          state of Rapid Eye Movements during sleep [syn: {paradoxical
          sleep}, {rapid eye movement sleep}, {REM sleep}, {rapid
          eye movement}]
     2: (Roentgen Equivalent Man) the dosage of ionizing radiation
        that will cause the same amount of injury to human tissue
        as 1 roentgen of X-rays

Source : Free On-Line Dictionary of Computing

REM
     
         (From "remark") The {keyword} used in {BASIC} to
        introduce a {comment} (which continues to the end of the
        line).  {MS-DOS} probably borrowed it from {BASIC}.  Might be
        used in the form "REM out" meaning to {comment out}.
     
        (1998-04-27)