buffalo vs American bison

buffalo and American bison both are nouns.

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

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

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

Other synonyms of buffalo include American buffalo, Bison bison.

buffalo (noun)	American bison (noun)
any of several Old World animals resembling oxen including, e.g., water buffalo, Cape buffalo	large shaggy-haired brown bison of North American plains
large shaggy-haired brown bison of North American plains
meat from an American bison

buffalo (verb)	American bison (verb)
intimidate or overawe