The Collaborative International Dictionary of English v.0.48:

Cracker \Crack"er\ (kr[a^]k"[~e]r), n.
   1. One who, or that which, cracks.
      [1913 Webster]

   2. A noisy boaster; a swaggering fellow. [Obs.]
      [1913 Webster]

            What cracker is this same that deafs our ears?
                                                  --Shak.
      [1913 Webster]

   3. A small firework, consisting of a little powder inclosed
      in a thick paper cylinder with a fuse, and exploding with
      a sharp noise; -- usually called firecracker.
      [1913 Webster]

   4. A thin, dry biscuit, often hard or crisp; as, a Boston
      cracker; a Graham cracker; a soda cracker; an oyster
      cracker.
      [1913 Webster]

   5. A nickname to designate a poor white in some parts of the
      Southern United States. --Bartlett.
      [1913 Webster]

   6. (Zool.) The pintail duck.
      [1913 Webster]

   7. pl. (Mach.) A pair of fluted rolls for grinding
      caoutchouc. --Knight.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cracker
    n 1: a thin crisp wafer made of flour and water with or without
         leavening and shortening; unsweetened or semisweet
    2: a poor White person in the southern United States [syn:
       redneck, cracker]
    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, cracker, 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: cracker, snapper, cracker bonbon]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "cracker":
   Brussels biscuit, Klaxon, Melba toast, backwoodsman, biscuit,
   boiler factory, boiler room, bone, briar-hopper, brush ape,
   bull-roarer, bushman, catcall, cherry bomb, clack, clacker,
   clam digger, clapper, cricket, desert rat, dust, firecracker,
   forester, frontiersman, graham cracker, hardtack, hillbilly,
   hinterlander, horn, mountain man, mountaineer, mummy, noisemaker,
   parchment, pilot biscuit, piny, pretzel, rattle, rattlebox,
   redneck, ridge runner, rusk, saltine, sea biscuit, ship biscuit,
   sinker, siren, snapper, soda cracker, steam whistle, stick,
   ticktack, wafer, whistle, whizgig, whizzer, woodlander, woodman,
   woodsman, zwieback



The Jargon File (version 4.4.7, 29 Dec 2003):

cracker
 n.

    One who breaks security on a system. Coined ca. 1985 by hackers in defense
    against journalistic misuse of hacker (q.v., sense 8). 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,
    benign, practical reasons (for example, if it's necessary to get around
    some security in order to get some work done).

    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 poly-culture this lexicon
    describes; though crackers often like to describe themselves as hackers,
    most true hackers consider them a separate and lower form of life. An easy
    way for outsiders to spot the difference is that crackers use grandiose
    screen names that conceal their identities. Hackers never do this; they
    only rarely use noms de guerre at all, and when they do it is for display
    rather than concealment.

    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. Some other reasons crackers are
    looked down on are discussed in the entries on cracking and phreaking.
    See also samurai, dark-side hacker, and hacker ethic. For a portrait
    of the typical teenage cracker, see warez d00dz.


The Free On-line Dictionary of Computing (30 December 2018):

cracker
cracking

    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)