crack a book
To open a book in order to study. Usually used with a negative.
John did not crack a book until the night before the exam.
Many students think they can pass without cracking a book.
crack a bottle
To open a new bottle of alcoholic beverage.
On birthdays it is customary to crack a bottle and offer one's best wishes.
crack a joke
To make a joke; tell a joke.
The men sat around the stove, smoking and cracking jokes.
crack a smile
To let a smile show on one's face; permit a smile to appear.
Bob told the whole silly story without even cracking a smile.
Scrooge was a gloomy man, who never cracked a smile.
When we gave the shy little boy an ice cream cone, he finally cracked a smile.
crack down
To enforce laws or rules strictly; require full obedience to a rule. Often used with on.
After a speeding driver hit a child, the police cracked down.
Police suddenly cracked down on the selling of liquors to minors.
The coach cracked down on the players when he found they had not been obeying the training rules.
crack of dawn
The time in the morning when the sun's rays first appear.
The rooster crows at the crack of dawn and wakes up everybody on the farm.
crack the whip
To get obedience or cooperation by threats of punishment.
If the children won't behave when I reason with them, I have to crack the whip.
crack up
To wreck or be wrecked; smash up.
The airplane cracked up in landing.
He cracked up his car.
To become mentally ill under physical or mental overwork or worry.
He had kept too busy for years, and when failures came, he cracked up.
It seemed to be family problems that made him crack up.
Burst into laughter or cause to burst into laughter.
That comedian cracks me up.