wildebeest vs gnu

wildebeest and gnu both are nouns.

Word	Noun	Adjective	Verb	Adverb
wildebeest	Yes	No	No	No
gnu	Yes	No	No	No

As nouns, wildebeest and gnu are synonyms defined as:

wildebeest and gnu: large African antelope having a head with horns like an ox and a long tufted tail

wildebeest (noun)	gnu (noun)
large African antelope having a head with horns like an ox and a long tufted tail	large African antelope having a head with horns like an ox and a long tufted tail