field day

Meaning

Noun

• A day for manoeuvres and tactical exercises in "the field".
• A school day for athletic events; a sports day.
• A day of class taken away from school for a field trip.
• A great time or a great deal to do; a period of bustling activity.
• A great time or a great deal to do, at somebody else's expense.
• A day on which there is top-to-bottom all-hands cleaning.

Origin

• Some postulate the idiomatic usage is derived from the "parade day" military use. A parade is much easier than the soldiers’ usual drilling and intense exercise.