Bison bison vs American buffalo

Bison bison and American buffalo both are nouns.

Word	Noun	Adjective	Verb	Adverb
Bison bison	Yes	No	No	No
American buffalo	Yes	No	No	No

As nouns, Bison bison and American buffalo are synonyms defined as:

Bison bison and American buffalo: large shaggy-haired brown bison of North American plains

Other synonyms of Bison bison include American bison, buffalo.

Bison bison (noun)	American buffalo (noun)
large shaggy-haired brown bison of North American plains	large shaggy-haired brown bison of North American plains