crack

noun

• 1a line on the surface of something along which it has split without breaking into separate parts:a hairline crack down the middle of the glass
• a narrow space between two surfaces, especially ones that have broken or been moved apart:he climbed into a crack between two rocks the door opened a tiny crack
• a vulnerable point; a flaw:the company spotted a crack in their rival’s defenses

• 2a sudden sharp or explosive noise:a loud crack of thunder
• a sharp blow, especially one that makes a noise: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:the boy’s voice had an uncertain crack in it

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

• 4 [in singular] informal an attempt to gain or achieve something:I thought I had a crack at winning
• a chance to attack or compete with someone: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.

verb

• 1break or cause to break without a complete separation of the parts: [no object]:the ice all over the lake had cracked [with object]:a stone cracked the headlight glass on his car
• break or cause to break open or apart: [no object]:you can see how the landmasses have cracked up and moved around figurativehis face cracked into a smile [with object]:she cracked an egg into the frying pan
• [with object] break (wheat or corn) into coarse pieces.
• [with object] open slightly:gingerly, he cracks open his door
• give way or cause to give way under torture, pressure, or strain: [no object]:the witnesses cracked and the truth came out [with object]:no one can crack them—they believe their story

• 2make or cause to make a sudden sharp or explosive sound: [no object]:a shot cracked across the ridge [with object]:he cracked his whip and galloped away
• [no object] knock against something, making a noise on impact:she winced as her knees cracked against metal
• [with object] hit (someone or something) hard, making a sharp noise: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:“I want to get away,” she said, her voice cracking

• 3 [with object] informal find a solution to; decipher or interpret:a hacker cracked the codes used in Internet software
• break into (a safe).

• 4 [with object] tell (a joke):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: (as noun cracking)catalytic cracking

adjective

• very good, especially at a specified activity or in a specified role:he is a crack shot crack troops