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

processor farm
farm

    A parallel processor where tasks are
   distributed, or "farmed out", by one "farmer" processor to
   several "worker" processors, and results are sent back to the
   farmer.  This arrangement is suitable for applications which
   can be partitioned into many separate, independent tasks, the
   canonical examples being ray tracing and the Mandelbrot
   set.  In order to be efficient, the extra time spent on
   communications must be small compared to the time spent
   processing each task.

   (2001-05-28)