killing time; passing time
Neutral or positive nuance: doing something enjoyable or useful to fill spare time.
I killed time playing a smartphone game on the train.
Shall we go for a walk to pass the time?
wasting time; time-waster
Negative nuance: doing something pointless or unproductive; often used critically.
That kind of meeting is just a waste of time.
I was just wasting time browsing the internet, and now it's already midnight.
Smartphone games make a good way to kill time.
I went for a walk just to kill time.
I killed time on my phone on the train.