To kill time is to do something unimportant while you wait. Kill time at the airport, just killing time, something to kill time.
The phrase admits the activity does not matter, which is what separates it from resting or from doing nothing on purpose. Airports and waiting rooms are designed around it, which is why they are full of shops.
1phrasekill timeTo do something unimportant while waiting.
“We had two hours before our train, so we walked around the market to kill time.”
kill time is a passing of time.
Also accepted in games: pass the time
Practised in Time & Calendar, Idioms