fool around

fool around or mess around or play around or monkey around  {v.},  {informal}

1. To spend time playing, fooling, or joking instead of being serious or working; waste time.

If you go to college, you must work, not fool around.

The boys fooled around all afternoon in the park.

Compare: CUT UP.

2. To treat or handle carelessly.

Bob cut himself by fooling around with a sharp knife.

Suzie says she wishes John would quit playing around with the girls and get married.

3. or fiddle around

To work or do something in an irregular or unplanned way; tinker.

Jimmy likes to monkey around with automobile engines.

Alice is fooling around with the piano in her spare time.

Compare: FUCK AROUND.