The opposite of anthropomorphic. When you theriomorphisize something, you instill it with the qualities of an animal. Many religious deities are constructed theiromorphically. Also, likening someone to a dog, snake, weasel, or other animal is theiromorphisizeation.

Historical aside: When the Nazis took control of Germany in 1933 they had to convert the rest of the German population to their ideology. The ensuing propaganda campaign included (as you can well guess) incessant derisions of Jews and Judaism. They referred to them as "rats" in countless films, posters, and documents. Theriomorphism is useful in dehumanizing.