Flock printing or flocking is a printing process in which short fibers of rayon, cotton, wool, or another natural or synthetic material are applied to an adhesive-coated surface. This adds a velvet or suede-like texture to the surface. Since the fibers can be dyed, flocking can also add color to a printed area.
The fibers used in the process are known as flock. They can be applied to paper, plastic, metal, textiles, and even glass.
Flock printing is an old technique that was already in use in China around 1000 BC. In Europe, it became popular during the Middle Ages.
More information on flocking can be found on this page.