fool around

US /fuːl əˈraʊnd/
UK /fuːl əˈraʊnd/
"fool around" picture
1.

to behave in a silly or playful way, often wasting time

:
Stop fooling around and get your work done.
The kids were fooling around in the backyard.
2.

to have a casual sexual relationship with someone

:
He was accused of fooling around with a colleague.
They were just fooling around, nothing serious.