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1. a line on the surface of something along which it has split without breaking into separate parts:

«…の» 割れ目, 裂け目, ひび «in, between»

e.g. a hairline crack down the middle of the glass.

a narrow space between two surfaces, especially ones that have broken or been moved apart:

【窓･カーテンなどの】すき間, 少しの開き «in» ; 〖a ～; 副詞的に〗 少し

e.g. he climbed into a crack between two rocks

e.g. the door opened a tiny crack.

a vulnerable point; a flaw:

【考え･制度･組織などの】欠陥, 問題点 «in»

e.g. the company spotted a crack in their rival's defenses.

2. a sudden sharp or explosive noise:

(雷･銃などの)鋭い音

e.g. a loud crack of thunder.

a sharp blow, especially one that makes a noise:

｟くだけて｠ (主に頭への)強打

e.g. she gave the thief a crack over the head with her rolling pin.

a sudden harshness or change in pitch in a person's voice:

(主に困惑した時の)(突然の)声の変調

e.g. the boy's voice had an uncertain crack in it.

3. informal a joke, typically a critical or unkind one.

｟くだけて｠ «…についての» きつい冗談; (少し無礼な)言い返し, ひやかし «about»

4. in singular informal an attempt to gain or achieve something:

｟くだけて｠ 〖単数形で〗 «…の» チャンス, 試み «at»

e.g. I thought I had a crack at winning.

a chance to attack or compete with someone:

e.g. he wanted to have a crack at the enemy.

5. (also crack cocaine) a hard, crystalline form of cocaine broken into small pieces and smoked.

クラック〘コカインを精製し粒状にした純度の高い麻薬〙

1. break or cause to break without a complete separation of the parts:

〈硬いものに〉ひびが入る; 割れる, 砕ける, 折れる (!breakと異なり, ばらばらにはならない)

e.g. no object : the ice all over the lake had cracked

〈人などが〉〈硬い物など〉にひびを入らせる; 〈卵･木の実など〉を割る, 砕く

e.g. with object : a stone cracked the headlight glass on his car.

break or cause to break open or apart:

e.g. figurative : his face cracked into a smile

e.g. with object : she cracked an egg into the frying pan

e.g. no object : you can see how the landmasses have cracked up and moved around.

with object break (wheat or corn) into coarse pieces.

with object open slightly:

e.g. gingerly, he cracks open his door.

give way or cause to give way under torture, pressure, or strain:

｟くだけて｠ 〈人･神経などが〉(過労･苦難などで)精神的にまいる, くじける(up); 〈組織･関係などが〉壊れる, だめになる(up)

e.g. no object : the witnesses cracked and the truth came out

e.g. with object : no one can crack them—they believe their story.

2. make or cause to make a sudden sharp or explosive sound:

〈物が〉(パチン･ピシッ･ポキンと)鋭い音を立てる

e.g. no object : a shot cracked across the ridge

〈人･物などが〉…をパシッ［ピシャッ, パチン］と鳴らす (!受け身にしない)

e.g. with object : he cracked his whip and galloped away.

no object knock against something, making a noise on impact:

〈物などが〉 «…に» (激しく)あたる, ぶつかる «against, on»

e.g. she winced as her knees cracked against metal.

with object hit (someone or something) hard, making a sharp noise:

〈人が〉 «…に» (偶然に)〈膝･頭など〉をぶつける, ぶち当てる «against, on» ; 〈人が〉〈人〉を強くなぐる, たたく

e.g. she cracked him across the forehead.

no object (of a person's voice, especially that of an adolescent boy or a person under strain) suddenly change in pitch:

〈声が〉(急に)調子が変わる, うわずる, かすれる

e.g. “I want to get away,” she said, her voice cracking.

3. with object informal find a solution to; decipher or interpret:

〈問題･暗号など〉を解く

e.g. a hacker cracked the codes used in Internet software.

break into (a safe).

(金を盗むために)〈金庫〉を破る; 〘コンピュ〙 〈ソフトウェアなど〉を不法にコピーする.

4. with object tell (a joke):

〈冗談〉を言う

e.g. he cracked jokes which she didn't find very funny.

5. with object decompose (hydrocarbons) by heat and pressure with or without a catalyst to produce lighter hydrocarbons, especially in oil refining:

〘化〙 〈化合物〉を熱分解する; 〈重油など〉を分留する.

e.g. (as noun cracking) : catalytic cracking.

adjective attributive

very good, especially at a specified activity or in a specified role:

〖名詞の前で〗一流の; 高度な訓練を受けた〈兵士･運動選手など〉

e.g. he is a crack shot

e.g. crack troops.

North American informal open a book and read it; study.

a time very early in the morning; daybreak.

a thunder peal announcing the Day of Judgment.

with negative informal asserted to be (used to indicate that someone or something has been described too favorably):

e.g. life on tour is not as glamorous as it's cracked up to be.

North American informal make jokes; wisecrack.

informal act quickly and energetically:

e.g. most tickets have been snapped up, so get cracking if you want one.

escape from or be missed by something organized to catch or deal with one:

e.g. fatherless kids were not allowed to fall through the cracks.

informal take severe measures against:

e.g. we need to crack down hard on workplaces that break safety regulations.

1. informal suffer an emotional breakdown under pressure.

2. informal (also crack someone up) burst or cause to burst into laughter.

Old English cracian‘make an explosive noise’; of Germanic origin; related to Dutch kraken and German krachen. crack (sense 4 of the noun) is from Irish craic ‘entertaining conversation’.