WordNet (r) 3.0 (2006):

REM
    n 1: a recurring sleep state during which dreaming occurs; a
         state of rapidly shifting eye movements during sleep [syn:
         paradoxical sleep, rapid eye movement sleep, REM
         sleep, rapid eye movement, REM]
    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

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

REM
       Ring Error Monitor


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

REM
       Remote Equipment Module


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

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)