Source : Webster's Revised Unabridged Dictionary (1913)

Spoiler \Spoil"er\, n.
   1. One who spoils; a plunderer; a pillager; a robber; a
      despoiler.

   2. One who corrupts, mars, or renders useless.

Source : WordNet®

spoiler
     n 1: a candidate with no chance of winning but who may draw
          enough votes to prevent one of the leading candidates
          from winning
     2: someone who takes spoils or plunder (as in war) [syn: {plunderer},
         {pillager}, {looter}, {despoiler}, {raider}, {freebooter}]
     3: someone who pampers or spoils by excessive indulgence [syn:
        {pamperer}, {coddler}, {mollycoddler}]
     4: an airfoil mounted on the rear of a car to reduce lift at
        high speeds
     5: a hinged airfoil on the upper surface of an aircraft wing
        that is raised to reduce lift and increase drag

Source : Free On-Line Dictionary of Computing

spoiler
     
        1. A remark which reveals important plot elements
        from books or movies, thus denying the reader (of the article)
        the proper suspense when reading the book or watching the
        movie.
     
        2. Any remark which telegraphs the solution of a problem or
        puzzle, thus denying the reader the pleasure of working out
        the correct answer (see also {interesting}).  Either sense
        readily forms compounds like "total spoiler", "quasi-spoiler"
        and even "pseudo-spoiler".
     
        By convention, {Usenet} news articles which are spoilers in
        either sense should contain the word "spoiler" in the Subject:
        line, or guarantee via various tricks that the answer appears
        only after several screens-full of warning, or conceal the
        sensitive information via {rot13}, or some combination of
        these techniques.
     
        [{Jargon File}]
     
        (1995-01-18)