(in the distillation of petroleum or the like) the process of breaking down certain hydrocarbons into simpler ones of lower boiling points by means of excess heat, distillation under pressure, etc., in order to give a greater yield of low-boiling products than could be obtained by simple distillation.Compare catalytic cracking.


extremely; unusually: We saw a cracking good match at the stadium.

adjective Informal.

done with precision; smart: A cracking salute from the honor guard.

Nearby words

  1. crackers,
  2. cracket,
  3. crackhead,
  4. crackhouse,
  5. crackie,
  6. crackjaw,
  7. crackle,
  8. crackleware,
  9. crackling,
  10. crackly


    get cracking. crack(def 54).

Origin of cracking

Middle English word dating back to 1250–1300; see origin at crack, -ing1, -ing2



verb (used without object)

to break without complete separation of parts; become fissured: The plate cracked when I dropped it, but it was still usable.
to break with a sudden, sharp sound: The branch cracked under the weight of the snow.
to make a sudden, sharp sound in or as if in breaking; snap: The whip cracked.
(of the voice) to break abruptly and discordantly, especially into an upper register, as because of weariness or emotion.
to fail; give way: His confidence cracked under the strain.
to succumb or break down, especially under severe psychological pressure, torture, or the like: They questioned him steadily for 24 hours before he finally cracked.
Chemistry. to decompose as a result of being subjected to heat.
Chiefly South Midland and Southern U.S. to brag; boast.
Chiefly Scot. to chat; gossip.

verb (used with object)

to cause to make a sudden sharp sound: The driver cracked the whip.
to break without complete separation of parts; break into fissures.
to break with a sudden, sharp sound: to crack walnuts.
to strike and thereby make a sharp noise: The boxer cracked his opponent on the jaw.
to induce or cause to be stricken with sorrow or emotion; affect deeply.
to utter or tell: to crack jokes.
to cause to make a cracking sound: to crack one's knuckles.
to damage, weaken, etc.: The new evidence against him cracked his composure.
to make mentally unsound.
to make (the voice) harsh or unmanageable.
to solve; decipher: to crack a murder case.
Informal. to break into (a safe, vault, etc.).
Chemistry. to subject to the process of cracking, as in the distillation of petroleum.
Informal. to open and drink (a bottle of wine, liquor, beer, etc.).


a break without complete separation of parts; fissure.
a slight opening, as between boards in a floor or wall, or between a door and its doorpost.
a sudden, sharp noise, as of something breaking.
the snap of or as of a whip.
a resounding blow: He received a terrific crack on the head when the branch fell.
Informal. a witty or cutting remark; wisecrack.
a break or change in the flow or tone of the voice.
Informal. opportunity; chance; try: Give him first crack at the new job.
a flaw or defect.
Also called rock. Slang. pellet-size pieces of highly purified cocaine, prepared with other ingredients for smoking, and known to be especially potent and addicting.
Masonry. check1(def 41).
a mental defect or deficiency.
a shot, as with a rifle: At the first crack, the deer fell.
a moment; instant: He was on his feet again in a crack.
Slang. a burglary, especially an instance of housebreaking.
Chiefly British. a person or thing that excels in some respect.
Slang: Vulgar. the vulva.
Chiefly Scot. conversation; chat.
British Dialect. boasting; braggadocio.
Archaic. a burglar.


first-rate; excellent: a crack shot.


with a cracking sound.

Verb Phrases

crack down, to take severe or stern measures, especially in enforcing obedience to laws or regulations: The police are starting to crack down on local drug dealers.
crack off, to cause (a piece of hot glass) to fall from a blowpipe or punty.
crack on, Nautical.
  1. (of a sailing vessel) to sail in high winds under sails that would normally be furled.
  2. (of a power vessel) to advance at full speed in heavy weather.
crack up, Informal.
  1. to suffer a mental or emotional breakdown.
  2. to crash, as in an automobile or airplane: He skidded into the telephone pole and cracked up.
  3. to wreck an automobile, airplane, or other vehicle.
  4. to laugh or to cause to laugh unrestrainedly: That story about the revolving door really cracked me up. Ed cracked up, too, when he heard it.

Origin of crack

before 1000; Middle English crak(k)en (v.), crak (noun), Old English cracian to resound; akin to German krachen, Dutch kraken (v.), and German Krach, Dutch krak (noun)

Related formscrack·a·ble, adjectivecrack·less, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for cracking

British Dictionary definitions for cracking



(prenominal) informal fast; vigorous (esp in the phrase a cracking pace)
get cracking informal to start doing something quickly or do something with increased speed

adverb, adjective

British informal first-class; excellenta cracking good match


the process in which molecules are cracked, esp the oil-refining process in which heavy oils are broken down into hydrocarbons of lower molecular weight by heat or catalysisSee also catalytic cracker



to break or cause to break without complete separation of the partsthe vase was cracked but unbroken
to break or cause to break with a sudden sharp sound; snapto crack a nut
to make or cause to make a sudden sharp soundto crack a whip
to cause (the voice) to change tone or become harsh or (of the voice) to change tone, esp to a higher register; break
informal to fail or cause to fail
to yield or cause to yieldto crack under torture
(tr) to hit with a forceful or resounding blow
(tr) to break into or force opento crack a safe
(tr) to solve or decipher (a code, problem, etc)
(tr) informal to tell (a joke, etc)
to break (a molecule) into smaller molecules or radicals by the action of heat, as in the distillation of petroleum
(tr) to open (esp a bottle) for drinkinglet's crack another bottle
(intr) Scot and Northern English dialect to chat; gossip
(tr) informal to achieve (esp in the phrase crack it)
(tr) Australian informal to find or catchto crack a wave in surfing
crack a smile informal to break into a smile
crack hardy or crack hearty Australian and NZ informal to disguise one's discomfort, etc; put on a bold front
crack the whip informal to assert one's authority, esp to put people under pressure to work harder


a sudden sharp noise
a break or fracture without complete separation of the two partsa crack in the window
a narrow opening or fissure
informal a resounding blow
a physical or mental defect; flaw
a moment or specific instantthe crack of day
a broken or cracked tone of voice, as a boy's during puberty
(often foll by at) informal an attempt; opportunity to tryhe had a crack at the problem
slang a gibe; wisecrack; joke
slang a person that excels
Scot and Northern English dialect a talk; chat
slang a processed form of cocaine hydrochloride used as a stimulant. It is highly addictive
Also: craic informal, mainly Irish fun; informal entertainmentthe crack was great in here last night
obsolete, slang a burglar or burglary
crack of dawn
  1. the very instant that the sun rises
  2. very early in the morning
a fair crack of the whip informal a fair chance or opportunity
crack of doom doomsday; the end of the world; the Day of Judgment


(prenominal) slang first-class; excellenta crack shot

Word Origin for crack

Old English cracian; related to Old High German krahhōn, Dutch kraken, Sanskrit gárjati he roars

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for cracking
Online Etymology Dictionary, © 2010 Douglas Harper

Science definitions for cracking



The process of breaking down complex chemical compounds by heating them. Sometimes a catalyst is added to lower the amount of heat needed for the reaction. Cracking is used especially for breaking petroleum molecules into shorter molecules and to extract low-boiling fractions, such as gasoline, from petroleum. See also hydrocracking.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Idioms and Phrases with cracking


In addition to the idioms beginning with crack

  • crack a book
  • crack a bottle
  • crack a joke
  • crack a smile
  • crack down
  • cracked up
  • crack of dawn
  • crack the whip
  • crack up

also see:

  • by jove (cracky)
  • fall between the cracks
  • get cracking
  • hard nut to crack
  • have a crack at
  • make a crack
  • not all it's cracked up to be
  • paper over (the cracks)
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.