have a fling
have a fling (with someone)
To have a brief, noncommittal sexual relationship (with someone). I had a few flings in college, but it was only after I graduated that I started having any serious relationships. The professor lost her job for having a fling with one of her students.
have a ˈfling(informal)
1 enjoy yourself without worrying or thinking seriously about anything, especially when it is the last opportunity you will have: Before I started training, I had one last fling and went to Paris with a group of friends for the weekend.
2 have a short sexual relationship with somebody: ‘Do you know Sally Taylor?’ ‘Yes, I know her quite well in fact. We had a bit of a fling a few years ago.’