a line on the surface of something along which it has split without breaking apart

a hairline crack down the middle of the glass

a sudden sharp or explosive noise

a loud crack of thunder

a joke, typically a critical or unkind one

he knew about the gossip and would make the odd crack

enjoyable social activity; a good time

he loved the crack, the laughing

an attempt to achieve something

I fancy having a crack at winning a fourth title

a potent hard crystalline form of cocaine broken into small pieces and inhaled or smoked

he uses crack and cocaine

a crack dealer

break or cause to break without a complete separation of the parts

the ice all over the bog had cracked

take care not to crack the glass

make or cause to make a sudden sharp or explosive sound

a shot cracked across the ridge

he cracked his whip and galloped away

find a solution to; decipher or interpret

the code will help you crack the messages

tell (a joke)

he cracked jokes which she didn't find very funny

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

catalytic cracking increases gasoline yields