Source : WordNet®

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

Source : Free On-Line Dictionary of Computing

CPU
     
         1. {central processing unit}.
     
        2. Occasionally used (although less and less) to refer to the
        {system unit}.
     
        (2000-08-10)