Fuck around
Definition 1 of 3
Pro Tip 1/3Informal Slang
Used among friends or peers in casual settings, but inappropriate in formal situations. 
We were just fucking around in the park, nothing serious.
Pro Tip 2/3Time Wasting
Can imply laziness or procrastination, often used to call someone out for being unproductive. 
He's always fucking around instead of finishing his tasks.
Pro Tip 3/3Negative Connotation
Usually expresses frustration or annoyance at someone not taking things seriously. 
If you keep fucking around, we'll never get this project done.