WordNet (r) 3.0 (2006):

central processing unit
    n 1: (computer science) the part of a computer (a microprocessor
         chip) that does most of the data processing; "the CPU and
         the memory form the central part of a computer to which the
         peripherals are attached" [syn: central processing unit,
         CPU, C.P.U., central processor, processor,
         mainframe]

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

central processing unit
CPU
processor

    (CPU, processor) The part of a
   computer which controls all the other parts.  Designs vary
   widely but the CPU generally consists of the control unit,
   the arithmetic and logic unit (ALU), registers, temporary
   buffers and various other logic.

   The control unit fetches instructions from memory and
   decodes them to produce signals which control the other parts
   of the computer.  These signals cause it to transfer data
   between memory and ALU or to activate peripherals to perform
   input or output.

   Various types of memory, including cache, RAM and ROM,
   are often considered to be part of the CPU, particularly in
   modern microprocessors where a single integrated circuit
   may contain one or more processors as well as any or all of
   the above types of memory.  The CPU, and any of these
   components that are in separate chips, are usually all located
   on the same printed circuit board, known as the
   motherboard.  This in turn is located in the system unit
   (sometimes incorrectly referred to as the "CPU").

   A parallel computer has several CPUs which may share other
   resources such as memory and peripherals.

   The term "processor" has to some extent replaced "CPU", though
   RAM and ROM are not logically part of the processor.

   List of processors
   (http://lldn.timesys.com/complete_list_of_processors).

   (2007-04-02)