Print out one copy per student.
Pass out game sheets to each student. Tell them to fill in as many Christmas and Holiday related words as they can, one for each letter of the alphabet. Tell them they have 3 minutes! (or whatever time you decide)
You can play whoever has the most in 3 minutes wins OR you can go around and have everyone say their answers, if someone has else has the same answer, they have to cross that one off the list (so the more original the better). You could have 2 points for a Double word, such as Candy Cane.
You can make the topic more detailed (only xmas songs, things you decorate with at xmas, things you eat during holiday season, winter activities).