No laughing matter means something likely to have serious consequences. Eg: Your failing in two subjects is no laughing matter.
To take a leaf out of someone’s book means to follow someone’s example. Eg: He took a leaf out of his father’s book and studied hard to become a doctor.
Handle with kid gloves means treat with great caution or tact. Eg: The crowd handled the lost child with kid gloves.
To kill time means to occupy oneself with some activity in order to pass time. Eg: She browsed through some books to kill time.
When the balloon goes up means when the action or trouble begins. Eg: When the balloon went up in the college, all students stayed away.
Save one’s bacon means escape death or injury. Eg: He saved his bacon by jumping aside at the right moment.
To rue the day means to regret bitterly a particular moment. Eg: She lived to rue the day she left him.
Fair to middling means good enough but not very good. Eg: Your assignment is fair to middling.
To have the edge on means to have an advantage over. Eg: The basketball player had the edge on his opponents due to his height.