The Collaborative International Dictionary of English v.0.48:

Buffer \Buff"er\ (b[u^]f"[~e]r), n. [Prop a striker. See
   Buffet a blow.]
   1. (Mech.)
      (a) An elastic apparatus or fender, for deadening the jar
          caused by the collision of bodies; as, a buffer at the
          end of a railroad car.
      (b) A pad or cushion forming the end of a fender, which
          receives the blow; -- sometimes called buffing
          apparatus.
          [1913 Webster]

   2. One who polishes with a buff.
      [1913 Webster]

   3. A wheel for buffing; a buff.
      [1913 Webster]

   4. A good-humored, slow-witted fellow; -- usually said of an
      elderly man. [Colloq.] --Dickens.
      [1913 Webster]

   5. (Chem.) a substance or mixture of substances which can
      absorb or neutralize a certain quantity of acid or base
      and thus keep the degree of acidity or alkalinity of a
      solution (as measured by pH) relatively stable. Sometimes
      the term is used in a medical context to mean antacid.
      [PJC]

   6. (Computers) a data storage device or portion of memory
      used to temporarily store input or output data until the
      receiving device is ready to process it.
      [PJC]

   7. any object or person that shields another object or person
      from harm, shock, or annoyance; as, the President's staff
      is his buffer from constant interruptions of his work.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

buffer \buff"er\ (b[u^]f"[~e]r), v. t. (Chem.)
   to add a buffer[5] to (a solution), so as to reduce unwanted
   fluctuation of acidity.
   [PJC]

WordNet (r) 3.0 (2006):

buffer
    n 1: (chemistry) an ionic compound that resists changes in its
         pH
    2: a neutral zone between two rival powers that is created in
       order to diminish the danger of conflict [syn: buffer zone,
       buffer]
    3: an inclined metal frame at the front of a locomotive to clear
       the track [syn: fender, buffer, cowcatcher, pilot]
    4: (computer science) a part of RAM used for temporary storage
       of data that is waiting to be sent to a device; used to
       compensate for differences in the rate of flow of data
       between components of a computer system [syn: buffer,
       buffer storage, buffer store]
    5: a power tool used to buff surfaces [syn: buffer,
       polisher]
    6: a cushion-like device that reduces shock due to an impact
       [syn: buffer, fender]
    7: an implement consisting of soft material mounted on a block;
       used for polishing (as in manicuring) [syn: buff, buffer]
    v 1: add a buffer (a solution); "buffered saline solution for
         the eyes"
    2: protect from impact; "cushion the blow" [syn: cushion,
       buffer, soften]

The Free On-line Dictionary of Computing (19 January 2023):

buffer

   1. An area of memory used for storing messages.  Typically, a
   buffer will have other attributes such as an input pointer
   (where new data will be written into the buffer), and output
   pointer (where the next item will be read from) and/or a count
   of the space used or free.  Buffers are used to decouple
   processes so that the reader and writer may operate at
   different speeds or on different sized blocks of data.

   There are many different algorithms for using buffers, e.g.
   first-in first-out (FIFO or shelf), last-in first-out (LIFO or
   stack), double buffering (allowing one buffer to be read while
   the other is being written), cyclic buffer (reading or writing
   past the end wraps around to the beginning).

   2. An electronic device to provide compatibility between two
   signals, e.g. changing voltage levels or current capability.