field day

noun6

1. •
   A day for maneuvers and tactical exercises in the field (across the landscape).
2. •
   A great time or a great deal to do; a period of bustling activity.

   • They went to the park and had a field day playing on the swings.
3. •
   A great time or a great deal to do, at somebody else's expense.

   • The reporters will have a field day with a comment like that.
   • The scandal was a field day for the press.
4. •
   (US) A school day for athletic events.
5. •
   A day of class taken away from school for a field trip.
6. •
   (US, Navy) A day on which there is top-to-bottom all-hands cleaning.