black buck vs blackbuck

black buck and blackbuck both are nouns.

Word	Noun	Adjective	Verb	Adverb
black buck	Yes	No	No	No
blackbuck	Yes	No	No	No

As nouns, black buck and blackbuck are synonyms defined as:

black buck and blackbuck: common Indian antelope with a dark back and spiral horns

Other synonyms of black buck include Antilope cervicapra.

black buck (noun)	blackbuck (noun)
common Indian antelope with a dark back and spiral horns	common Indian antelope with a dark back and spiral horns