Source : Webster's Revised Unabridged Dictionary (1913)

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}.]
   1. To break or burst, with or without entire separation of
      the parts; as, to crack glass; to crack nuts.

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

            O, madam, my old heart is cracked.    --Shak.

            He thought none poets till their brains were
            cracked.                              --Roscommon.

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

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

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

   {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.]

Crack \Crack\, v. i.
   1. To burst or open in chinks; to break, with or without
      quite separating into parts.

            By misfortune it cracked in the coling. --Boyle.

            The mirror cracked from side to side. --Tennyson.

   2. To be ruined or impaired; to fail. [Collog.]

            The credit . . . of exchequers cracks, when little
            comes in and much goes out.           --Dryden.

   3. To utter a loud or sharp, sudden sound.

            As thunder when the clouds in autumn crack. --Shak.

   4. To utter vain, pompous words; to brag; to boast; -- with
      of. [Archaic.]

            Ethoipes of their sweet complexion crack. --Shak.

Crack \Crack\, n.
   1. A partial separation of parts, with or without a
      perceptible opening; a chink or fissure; a narrow breach;
      a crevice; as, a crack in timber, or in a wall, or in
      glass.

   2. Rupture; flaw; breach, in a moral sense.

            My love to thee is sound, sans crack or flaw.
                                                  --Shak.

   3. A sharp, sudden sound or report; the sound of anything
      suddenly burst or broken; as, the crack of a falling
      house; the crack of thunder; the crack of a whip.

            Will the stretch out to the crack of doom? --Shak.

   4. The tone of voice when changed at puberty.

            Though now our voices Have got the mannish crack.
                                                  --Shak.

   5. Mental flaw; a touch of craziness; partial insanity; as,
      he has a crack.

   6. A crazy or crack-brained person. [Obs.]

            I . . . can not get the Parliament to listen to me,
            who look upon me as a crack and a projector.
                                                  --Addison.

   7. A boast; boasting. [Obs.] ``Crack and brags.'' --Burton.
      ``Vainglorius cracks.'' --Spenser.

   8. Breach of chastity. [Obs.] --Shak.

   9. A boy, generally a pert, lively boy. [Obs.]

            Val. 'T is a noble child. Vir. A crack, madam.
                                                  --Shak.

   10. A brief time; an instant; as, to be with one in a crack.
       [Eng. & Scot. Colloq.]

   11. Free conversation; friendly chat. [Scot.]

             What is crack in English? . . . A crack is . . . a
             chat with a good, kindly human heart in it. --P. P.
                                                  Alexander.

Crack \Crack\, a.
   Of superior excellence; having qualities to be boasted of.
   [Colloq.]

         One of our crack speakers in the Commons. --Dickens.

Source : WordNet®

crack
     adj : of the highest quality; "an ace reporter"; "a crack shot";
           "a first-rate golfer"; "a super party"; "played
           top-notch tennis"; "an athlete in tiptop condition";
           "she is absolutely tops" [syn: {ace}, {A-one}, {first-rate},
            {super}, {tiptop}, {topnotch}, {tops(p)}]

crack
     n 1: a long narrow opening [syn: {cleft}, {crevice}, {fissure}, {scissure}]
     2: a narrow opening; "he opened the window a crack" [syn: {gap}]
     3: a long narrow depression in a surface [syn: {crevice}, {cranny},
         {fissure}, {chap}]
     4: 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: {cracking}, {snap}]
     5: a chance to do something; "he wanted a shot at the champion"
        [syn: {shot}]
     6: witty remark [syn: {wisecrack}, {sally}, {quip}]
     7: a blemish resulting from a break without complete separation
        of the parts; "there was a crack in the mirror"
     8: a purified and potent form of cocaine that is smoked rather
        than snorted [syn: {tornado}]
     9: a usually brief attempt; "he took a crack at it"; "I gave it
        a whirl" [syn: {fling}, {go}, {pass}, {whirl}, {offer}]
     10: the act of cracking something [syn: {fracture}, {cracking}]

crack
     v 1: become fractured; break or crack on the surface only; "The
          glass cracked when it was heated" [syn: {check}, {break}]
     2: make a very sharp explosive sound; "His gun cracked"
     3: make a sharp sound; "his fingers snapped" [syn: {snap}]
     4: hit forcefully; deal a hard blow, making a cracking noise;
        "The teacher cracked him across the face with a ruler"
     5: pass through (a barrier); "Registrations cracked through the
        30,000 mark in the county" [syn: {break through}]
     6: break partially but keep its integrity; "The glass cracked"
     7: break suddenly and abruptly, as under tension; "The rope
        snapped" [syn: {snap}]
     8: suffer a nervous breakdown [syn: {crack up}, {crock up}, {break
        up}, {collapse}]
     9: tell spontaneously; "crack a joke"
     10: cause to become cracked; "heat and light cracked the back of
         the leather chair"
     11: reduce (petroleum) to a simpler compound by cracking
     12: break into simpler molecules by means of heat; "The
         petroleum cracked"