The Collaborative International Dictionary of English v.0.48:

Crack \Crack\ (kr[a^]k), v. t. [imp. & p. p. Cracked
   (kr[a^]kt); p. pr. & vb. n. Cracking.] [OE. cracken,
   craken, to crack, break, boast, AS. cracian, cearcian, to
   crack; akin to D. kraken, G. krachen; cf. Skr. garj to
   rattle, or perh. of imitative origin. Cf. Crake,
   Cracknel, Creak.]
   [1913 Webster]
   1. To break or burst, with or without entire separation of
      the parts; as, to crack glass; to crack nuts.
      [1913 Webster]

   2. To rend with grief or pain; to affect deeply with sorrow;
      hence, to disorder; to distract; to craze.
      [1913 Webster]

            O, madam, my old heart is cracked.    --Shak.
      [1913 Webster]

            He thought none poets till their brains were
            cracked.                              --Roscommon.
      [1913 Webster]

   3. To cause to sound suddenly and sharply; to snap; as, to
      crack a whip.
      [1913 Webster]

   4. To utter smartly and sententiously; as, to crack a joke.
      --B. Jonson.
      [1913 Webster]

   5. To cry up; to extol; -- followed by up. [Low]
      [1913 Webster]

   To crack a bottle, to open the bottle and drink its
      contents.

   To crack a crib, to commit burglary. [Slang]

   To crack on, to put on; as, to crack on more sail, or more
      steam. [Colloq.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

cracking \cracking\ n.
   1. the act of cracking something.

   Syn: fracture, crack.
        [WordNet 1.5]

   2. (Chem.) the process of making lower molecular weight
      hydrocarbons from heavier hydrocarbons in petroleum, by
      exposure to heat and catalysts. It is used to convert
      heavier alkanes into gasoline, or to improve the octane
      number of an alkane mixture.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

cracking \cracking\ adj.
   same as groovy, sense 1. [informal]

   Syn: bang-up, bully, cool, corking, dandy, great, groovy,
        keen, neat, nifty, not bad(predicate), peachy, slap-up,
        swell, smashing.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

cracking
    adj 1: very good; "he did a bully job"; "a neat sports car";
           "had a great time at the party"; "you look simply
           smashing" [syn: bang-up, bully, corking,
           cracking, dandy, great, groovy, keen, neat,
           nifty, not bad(p), peachy, slap-up, swell,
           smashing]
    n 1: a sudden sharp noise; "the crack of a whip"; "he heard the
         cracking of the ice"; "he can hear the snap of a twig"
         [syn: crack, cracking, snap]
    2: the act of cracking something [syn: fracture, crack,
       cracking]
    3: the process whereby heavy molecules of naphtha or petroleum
       are broken down into hydrocarbons of lower molecular weight
       (especially in the oil-refining process)

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

cracking
 n.

    [very common] The act of breaking into a computer system; what a cracker
    does. Contrary to widespread myth, this 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 incompetent as hackers. This entry used to say 'mediocre', but
    the spread of rootkit and other automated cracking has depressed the
    average level of skill among crackers.


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)