Killing time

It's means to do something which it's not really important just to keep you occupied until the start of your next plan or arrangement.
Ex:
1. I turned up an hour early for my flight, so I just look at the duty free to kill some time.
2. I had an hour between work and meeting my friends so I killed time in department store.
3. I always arrives hours early for job interviews. I'd have rather to kill time than deal with the stress of being late.