0 especially in the past, a person who takes part in 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): --
On Twelfth Night wassailers hang toasted bread on their most productive apple tree to attract the robins which are traditionally held to be good spirits.
The tradition of wassailers going from door to door, singing and drinking the health of those they visited went back to medieval times.
We may now be more likely to hear them blasting out of supermarket sound systems than from the lips of wassailers in the streets, but carols remain central to the experience of Christmas.
Boisterous wassailers are one reason why Oliver Cromwell and Long Parliament passed an ordinance in 1647 that essentially banned Christmas.