Source : WordNet®

central processing unit
     n : (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: {CPU}, {C.P.U.}, {central
         processor}, {processor}, {mainframe}]

Source : Free On-Line Dictionary of Computing

central processing unit
     
         (CPU, processor) The part of a
        computer which controls all the other parts.  Designs vary
        widely but, in general, the CPU consists of the {control
        unit}, the {arithmetic and logic unit} (ALU) and memory
        ({registers}, {cache}, {RAM} and {ROM}) as well as various
        temporary buffers and other logic.
     
        The control unit fetches instructions from memory and decodes
        them to produce signals which control the other part of the
        computer.  This may cause it to transfer data between memory
        and ALU or to activate {peripherals} to perform input or
        output.
     
        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 normally considered as part of a
        processor.  This is particularly true of common modern
        {microprocessors} though there have been microprocessors which
        include RAM and/or ROM on the same {integrated circuit}.
     
        The {CPU Info Center} lists many kinds of CPU.
     
        (1998-10-21)