WordWeb Online

1. Behave in a foolish, fun way; indulge in horseplay
   "Enough fooling around--let's get back to work!";
   - horse around, arse around [Brit, Cdn, informal], fool, muck around [Brit, informal], muck about [Brit, informal], arse about [Brit, Cdn, informal], kid around [informal], screw around [informal]
    
2. Commit adultery
   "he fools around a lot";
   - play around

Derived forms: fools around, fooling around, fooled around

Type of: betray, cheat, cheat on, cuckold, jest, joke, play, wander