Source : Webster's Revised Unabridged Dictionary (1913)

Accumulator \Ac*cu"mu*la`tor\, n. [L.]
   1. One who, or that which, accumulates, collects, or amasses.

   2. (Mech.) An apparatus by means of which energy or power can
      be stored, such as the cylinder or tank for storing water
      for hydraulic elevators, the secondary or storage battery
      used for accumulating the energy of electrical charges,
      etc.

   3. A system of elastic springs for relieving the strain upon
      a rope, as in deep-sea dredging.

Source : WordNet®

accumulator
     n 1: a person who is employed to collect payments (as for rent or
          taxes) [syn: {collector}, {gatherer}]
     2: a voltaic battery that stores electric charge [syn: {storage
        battery}]
     3: (computer science) a register that has a built-in adder that
        adds an input number to the contents of the accumulator
        [syn: {accumulator register}]

Source : Free On-Line Dictionary of Computing

accumulator
     
         In a {central processing unit}, a {register} in
        which intermediate results are stored.  Without an
        accumulator, it would be necessary to write the result of each
        calculation (addition, multiplication, {shift}, etc.) to {main
        memory} and read them back.  Access to main memory is slower
        than access to the accumulator which usually has direct paths
        to and from the {arithmetic and logic unit} (ALU).
     
        The {canonical} example is summing a list of numbers.  The
        accumulator is set to zero initially, each number in turn is
        added to the value in the accumulator and only when all
        numbers have been added is the result written to main memory.
     
        Modern CPUs usually have many registers, all or many of which
        can be used as accumulators.  For this reason, the term
        "accumulator" is somewhat archaic.  Use of it as a synonym for
        "register" is a fairly reliable indication that the user has
        been around for quite a while and/or that the architecture
        under discussion is quite old.  The term in full is almost
        never used of microprocessor registers, for example, though
        symbolic names for arithmetic registers beginning in "A"
        derive from historical use of the term "accumulator" (and not,
        actually, from "arithmetic").  Confusingly, though, an "A"
        register name prefix may also stand for "address", as for
        example on the {Motorola} {680x0} family.
     
        2.  A register, memory location or variable being
        used for arithmetic or logic (as opposed to addressing or a
        loop index), especially one being used to accumulate a sum or
        count of many items.  This use is in context of a particular
        routine or stretch of code.  "The FOOBAZ routine uses A3 as an
        accumulator."
     
        [{Jargon File}]
     
        (1999-04-20)