Source : Webster's Revised Unabridged Dictionary (1913)

Cracker \Crack"er\ (kr[a^]k"[~e]r), n.
   1. One who, or that which, cracks.

   2. A noisy boaster; a swaggering fellow. [Obs.]

            What cracker is this same that deafs our ears?
                                                  --Shak.

   3. A small firework, consisting of a little powder inclosed
      in a thick paper cylinder with a fuse, and exploding with
      a sharp noise; -- often called {firecracker}.

   4. A thin, dry biscuit, often hard or crisp; as, a Boston
      cracker; a Graham cracker; a soda cracker; an oyster
      cracker.

   5. A nickname to designate a poor white in some parts of the
      Southern United States. --Bartlett.

   6. (Zo["o]l.) The pintail duck.

   7. pl. (Mach.) A pair of fluted rolls for grinding
      caoutchouc. --Knight.

Source : WordNet®

cracker
     n 1: a thin crisp wafer made or flour and water with or without
          leavening and shortening; unsweetened or semisweet
     2: a poor white person in the southern United States [syn: {redneck}]
     3: a programmer who `cracks' (gains unauthorized access to)
        computers, typically to do malicious things; "crackers are
        often mistakenly called hackers"
     4: firework consisting of a small explosive charge and fuse in
        a heavy paper casing [syn: {firecracker}, {banger}]
     5: a party favor consisting of a paper roll (usually containing
        candy or a small favor) that pops when pulled at both ends
        [syn: {snapper}, {cracker bonbon}]

Source : Free On-Line Dictionary of Computing

cracker
     
         An individual who attempts to gain unauthorised
        access to a computer system.  These individuals are often
        malicious and have many means at their disposal for breaking
        into a system.  The term was coined ca. 1985 by hackers in
        defence against journalistic misuse of "{hacker}".  An earlier
        attempt to establish "worm" in this sense around 1981--82 on
        {Usenet} was largely a failure.
     
        Use of both these neologisms reflects a strong revulsion
        against the theft and vandalism perpetrated by cracking rings.
        The neologism "cracker" in this sense may have been influenced
        not so much by the term "safe-cracker" as by the non-jargon
        term "cracker", which in Middle English meant an obnoxious
        person (e.g., "What cracker is this same that deafs our ears /
        With this abundance of superfluous breath?"  -- Shakespeare's
        King John, Act II, Scene I) and in modern colloquial American
        English survives as a barely gentler synonym for "white
        trash".
     
        While it is expected that any real hacker will have done some
        playful cracking and knows many of the basic techniques,
        anyone past {larval stage} is expected to have outgrown the
        desire to do so except for immediate practical reasons (for
        example, if it's necessary to get around some security in
        order to get some work done).
     
        Contrary to widespread myth, cracking does not usually involve
        some mysterious leap of hackerly brilliance, but rather
        persistence and the dogged repetition of a handful of fairly
        well-known tricks that exploit common weaknesses in the
        security of target systems.  Accordingly, most crackers are
        only mediocre hackers.
     
        Thus, there is far less overlap between hackerdom and
        crackerdom than the {mundane} reader misled by
        sensationalistic journalism might expect.  Crackers tend to
        gather in small, tight-knit, very secretive groups that have
        little overlap with the huge, open hacker poly-culture; though
        crackers often like to describe *themselves* as hackers, most
        true hackers consider them a separate and lower form of life,
        little better than {virus} writers.  Ethical considerations
        aside, hackers figure that anyone who can't imagine a more
        interesting way to play with their computers than breaking
        into someone else's has to be pretty {losing}.
     
        See also {Computer Emergency Response Team}, {dark-side
        hacker}, {hacker ethic}, {phreaking}, {samurai}, {Trojan
        Horse}.
     
        [{Jargon File}]
     
        (1998-06-29)