What is a reveller?

"Revel" as a verb means to celebrate, so even people at a cocktail party of tailgate party could be called revellers.

There are also traditional revels associated with certain times of year, such as midwinter and spring. In Britain and continental Europe, midwinter revels have a long history, and predate the time that Christians decided to observe the birth of Jesus in December. Over time, those customs merged. Songs, dances, and mummer plays became part of the custom.

In the U.S., there are several local groups that do a Christmas Revels as a theatrical production. See www.revels.org.