0 especially in the past, the activity of going from house to house at Christmas time singing carols (= Christmas songs), traditionally drinking wassail (= warm beer or wine with spices added): --
In parts of England people still worship Pomona, the Roman goddess of fruit trees, through the custom of wassailing, which is intended to encourage a good crop of apples.
As befitted their name, the Puritans found feasting, wassailing, gift giving, and wishing one another a merry Christmas ungodly and sinful.
If you're interested in engaging in some good, old-fashioned wassailing, the original lyrics to Here We Come a-Wassailing are a helpful guide.