1 BREAK (I, T) to break or make something break so that it gets one or more lines on its surface: Don't put that delicate china in the dishwasher - it may crack. | She fell off her bike and cracked a bone in her leg.2 LOUD SOUND (I, T) to make a sudden quick sound like the sound of something breaking, or to make something do this: The branch cracked loudly and broke off. | He had a habit of cracking his knuckles.3 HIT STH (intransitive always + adv/prep, transitive always + adv/prep) to hit something hard but not deliberately, especially part of your body(+ against/on): The rock cracked against my shoulder. | crack sth against/on: He fell, cracking his head on the wall.4 HIT SB (T) to hit someone hard and deliberately on part of their body: crack sb over/in/on: He cracked the burglar over the head with a vase.5 LOSE CONTROL also crack up (I) to be unable to continue doing something or working well because of great pressure: We're hoping the prisoner will crack under interrogation. | The whole political system is beginning to crack up.6 MENTALLY ILL also crack up (I) to become mentally ill because of too much pressure: Many of the soldiers cracked up on returning from the war.7 VOICE (I) if your voice cracks, it changes from one level to another suddenly because of strong emotions: Her voice cracked as she tried to explain what had happened.8 NERVE (I) if your nerve cracks, you no longer feel confident that you can do something difficult: At the last moment his nerve cracked.9 EGG/NUT (T) to break the outside part of something, such as an egg or a nut, in order to get what is inside it: The foxes crack the eggs, and suck out the yolk.10 STEAL (T) to open a safe 2 illegally, in order to steal what is inside11 SOLVE (T) to find the answer to a problem or find how to use a code 1 (4): His skill at cracking codes proved invaluable during the war. | This is a national problem, we're not going to crack it here this afternoon.12 STOP CRIME/ENEMY (T) to find a way of destroying an enemy or stopping something they are doing: Police are hoping to crack the drug-smuggling ring.13 crack it BrE to succeed in some way14 crack a deal AmE informal to succeed in making a business deal, especially when this has been difficult: We finally managed to crack that deal with the Japanese.15 crack a joke informal to tell a joke: He kept cracking jokes about my appearance.16 crack a smile AmE informal to smile when you have been serious, sad, or angry: She finally cracked a smile, although she had tears in her eyes.17 crack open a bottle informal to open a bottle of alcohol for drinking: Let's crack open a bottle to celebrate!18 not all/everything it's cracked up to be informal not as good as people say it is: The film wasn't all it's cracked up to be - I was quite bored in parts.19 get cracking informal to start doing something or going somewhere as quickly as possible: The train goes at ten so let's get cracking.20 crack the whip informal to make people you have control over work very hardcrack down phrasal verb (I) to become more strict in dealing with a problem and punishing the people involved (+ on): The police are cracking down on illegal parking. -see also: crackdown crack on phrasal verb (I) BrE informal to continue working hard at something in order to try to finish it (+ with): I'm hoping to crack on with that translation this weekend. crack up phrasal verb informal1 (I, T) to laugh a lot at something, or to make someone laugh a lot: Everyone in the class just cracked up. | crack sb up: She's so funny. She cracks me up.2 (I) to become unable to think or behave sensibly because you have too many problems, too much work etc: I must be cracking up - I've lost those papers again!-see also: crack-up 2 noun (C)1 THIN SPACE a very narrow space between two things or two parts of something(+ in): A thin ray of light shone through a crack in the curtains. (+ between): The children carefully avoided the cracks between the paving stones. | open sth a crack (=open something very slightly): She opened the door a crack and peeped out.2 BREAK a thin line on the surface of something when it is broken but has not actually come apart(+ in): There were several cracks in the glass.3 PROBLEM a fault in an idea, system, or organization(+ in): Cracks were appearing in the government's economic policy.4 SOUND a sudden loud very sharp sound like the sound of a stick being broken: There was a loud crack as the wood finally broke in two.5 JOKE/REMARK a clever joke or rude remark(+ about): I've had enough of your cracks about my weight. | make a crack: I wish I hadn't made that crack about lawyers.6 CHANCE TO DO STH informal an opportunity or attempt to achieve something, especially for the first time(+ at): I'd like a crack at climbing that mountain. | have/take a crack at sth: Why don't you have a crack at that competition - you might win! | a (fair) crack of the whip BrE (=a chance to do something or be in control): They'll do well if we give them a fair crack of the whip.7 a crack on the head what you feel when you are hit on the head, usually not deliberately: I got a nasty crack on the head as I went through the low doorway.8 a crack in sb's voice a sudden change in the level of someone's voice, especially because they are very upset: He noticed the crack in her voice as she tried to continue.9 crack of dawn very early in the morning: We'll have to get up at the crack of dawn tomorrow.10 DRUG (U) a very pure form of the drug cocaine that some people take illegally for pleasure11 good crack IrE, BrE spoken friendly, enjoyable talk in a group: We go there for the crack.12 what's the crack? BrE spoken used to ask someone what is happening, or what has been happening recently-see also: paper over the cracks paper 3 (2) 3 adjective (only before noun)1 having a very high level of quality or skill, or being very highly trained: A crack regiment was sent in to deal with the situation.2 crack shot someone who always hits what they shoot at
Longman dictionary of contemporary English. 2004.