Here is one definition:
A special event is a gathering of human beings, generally lasting from a few hours to a few days, designed to celebrate, honor, discuss, sell, teach about, encourage, observe, or influence human endeavors.
[Doug Matthews, Special Event Production (2016)]
To flesh this out a bit more, these characteristics are what turn an ordinary event in a "special event:"
- Must be of limited and fixed duration, typically hours or days at most.
- Must be a one-off or infrequent occurrence, typically monthly or annually at most.
- If part of a regular series, they must be an unusual component of the series.
- Must be unique.
- Must require one or more organizers.
- Execution must be planned and controlled.
- Must conform to the definition of a special event.
- Must be a live audience other than the organizers present at the physical event location.
