Revelry is a wild, fun time. If you enjoy the revelry of a New Year's Eve party, you might pay for partying hard the next day.
The noun revelry means merrymaking, but because it comes from the French word reveler meaning to rebel, its tone indicates carousing or noisy partying. It's not your grandparents' tame, sedate cocktail party: revelry is a full-throttle festive gathering, where people outwardly enjoy themselves. In fact, a wild party was once called a "revel," though you don't hear that term used much today.