to do something that keeps you busy while you are waiting for something else to happen
Are you really watching that nonsense movie or just trying to kill your time?
8. kill time/an hour etc to spend time doing something which is not important, while you are waiting to do something important or waiting for something else to happen:
With time to kill, he took a cab to the centre.
kill ˈtime | kill an ˈhour, a couple of ˈhours, etc. idiom
to spend time doing sth that is not important while you are waiting for sth else to happen
• We killed time playing cards.
Cambridge Advanced Learner's Dictionary - 4th Edition
kill time, an hour, etc.
B2 to do something that keeps you busy while you are waiting for something else to happen:
The train was late, so I killed an hour or so window-shopping.