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

CMYK
       Cyan Magenta Yellow blacK (color system, DTP)


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

CMYK

    cyan, magenta, yellow, key.

   A colour model that describes each colour in terms of the
   quantity of each secondary colour (cyan, magenta, yellow), and
   "key" (black) it contains.  The CMYK system is used for
   printing.  For mixing of pigments, it is better to use the
   secondary colours, since they mix subtractively instead of
   additively.  The secondary colours of light are cyan, magenta
   and yellow, which correspond to the primary colours of pigment
   (blue, red and yellow). In addition, although black could be
   obtained by mixing these three in equal proportions, in
   four-colour printing it always has its own ink.  This gives
   the CMYK model.  The K stands for "Key' or 'blacK,' so as not
   to cause confusion with the B in RGB.

   Alternative colour models are RGB and HSB.

   (1994-12-22)