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

greek
greeking

   1.  To display text as abstract dots and lines
   in order to give a preview of layout without actually being
   legible.  This is faster than drawing the characters correctly
   which may require scaling or other transformations.  Greeking
   is particularly useful when displaying a reduced image of a
   document where the text would be too small to be legible on
   the display anyway.

   A related technique is lorem ipsum.

   (2006-09-18)