There are many useful and fun expressions about time.
Time is money, time flies, you can run out of time or just waste it.
You can even kill it. Well, not really.
“To kill time” means to do something instead of just waiting to pass the time.
ex1. Usually I play games on my phone to kill time.
ex2. I missed my bus and had to wait for three hours for the next one, so I went to the shopping centre nearby to kill time.