1. a day devoted to outdoor sports or athletic contests, as at a school.
2. an outdoor gathering; outing; picnic.
3. a day for military exercises and display.
4. an occasion or opportunity for unrestricted activity, amusement, etc.: The children had a field day with their new skateboards.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.