"Flocking" a Christmas tree means to cover it with a thin layer of fake snow, creating a whimsical and nostalgic look. It can be achieved by using a special spray that is designed to adhere to the branches of the tree, creating a realistic snow effect. The term "flocking" comes from the traditional method of covering trees with real snow, which can be messy and difficult to maintain. With the advent of flocking sprays, however, it's now much easier to create a realistic and festive snow-covered tree in just a few simple steps.