The Collaborative International Dictionary of English v.0.48:

antacid \ant*ac"id\ ([a^]nt*[a^]s"[i^]d), antiacid
\an*ti*ac"id\([a^]n*t[-e]*[a^]s"[i^]d), n. [Pref. anti- + acid.]
   (Med.)
   A remedy for neutralizing acidity, especially of the stomach,
   as an alkali or absorbent. -- a. Counteractive of acidity.
   [1913 Webster + AS]

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]

WordNet (r) 3.0 (2006):

antacid
    adj 1: acting to neutralize acid (especially in the stomach)
    n 1: an agent that counteracts or neutralizes acidity
         (especially in the stomach) [syn: antacid, gastric
         antacid, alkalizer, alkaliser, antiacid]