However, depending on the context, you could use some informal terms:
* "Bison": This is the scientific term for buffalo, and while not strictly slang, it's more casual than the formal "American bison".
* "Beefalo": This is a crossbreed between a buffalo and a cow, and it's sometimes used informally to refer to buffalo in general.
* "Big fella": This is a general term for a large animal, and could be used to describe a buffalo.
* "Rug": This is a slang term for a buffalo hide, but it could be used to refer to the animal itself in a humorous or informal context.
Ultimately, the best term to use depends on the specific situation and your audience.