WordNet (r) 3.0 (2006):

microprocessor
    n 1: integrated circuit semiconductor chip that performs the
         bulk of the processing and controls the parts of a system;
         "a microprocessor functions as the central processing unit
         of a microcomputer"; "a disk drive contains a
         microprocessor to handle the internal functions of the
         drive"

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

microprocessor
micro

    (Or "micro") A computer whose entire CPU is
   contained on one (or a small number of) integrated circuits.

   The important characteristics of a microprocessor are the
   widths of its internal and external address bus and data
   bus (and instruction), its clock rate and its instruction
   set.  Processors are also often classified as either RISC
   or CISC.

   The first commercial microprocessor was the Intel 4004 which
   appeared in 1971.  This was the CPU member of a set of four
   LSI integrated circuits called the MCS-4, which was
   originally designed for use in a calculator but was marketed
   as "programmable controller for logic replacement".  The 4004
   is referred to as a 4-bit microprocessor since it processed
   only 4 bits of data at a time.  This very short word size is
   due mainly to the limitations imposed by the maximum
   integrated circuit density then achievable.

   As integrated circuit densities increased with the rapid
   development of integrated circuit manufacturing technology,
   the power and performance of the microprocessors also
   increased.  This is reflected in the increase in the CPU word
   size to 4, 8, 16, and by mid-1980s, 32 bits.  The smaller
   microprocessors have relatively simple instruction sets,
   e.g., no floating point instructions, but they are
   nevertheless suitable as controllers for a very wide range of
   applications such as car engines and microwave ovens.

   The Intel 4004 was followed with, among others the 4040,
   8008, 8080, 8086, 80186, 80286, 80386, 486 and
   Pentium.  Other families include the Motorola 6800 and
   680x0 families, National Semiconductor 16000 and National
   Semiconductor 32000, SPARC, ARM, MIPS, Zilog Z8000,
   PowerPC and the Inmos Transputer family.

   The larger, more recent microprocessors families have
   gradually acquired most of the features of large computers.
   As the microprocessor industry has matured, several families
   of microprocessors have evolved into de facto industrial
   standards with multiple manufacturers and numerous "support"
   chips including RAM, ROM, I/O controllers etc.

   A single chip microprocessor may include other components such
   as memory (RAM, ROM, PROM), memory management,
   caches, floating-point unit, input/output ports and
   timers.  Such devices are also known as microcontrollers.

   The one-chip microcomputer is in many respects, a landmark
   development in computer technology because it reduces the
   computer to a small, inexpensive, and easily replaceable
   design component.

   Microcomputers have given rise to a new class of
   general-purpose machines called personal computers.  These
   are small low cost computers that are designed to sit on an
   ordinary office desk or to be portable and fuelled the
   computer boom of the late 1980s.  The most widespread example
   is the also IBM PC, based on microprocessors from Intel
   Corporation.  Apple Computers, Inc. have also produced a
   range of personal computers, as have several other companies.

   See also killer micro, minicomputer, CPU Info Center.

   (2002-07-16)