bush baby vs lemur

bush baby and lemur both are nouns.

Word	Noun	Adjective	Verb	Adverb
bush baby	Yes	No	No	No
lemur	Yes	No	No	No

As nouns, lemur is a hypernym of bush baby; that is, lemur is a word with a broader meaning than bush baby:

bush baby: agile long-tailed nocturnal African lemur with dense woolly fur and large eyes and ears
lemur: large-eyed arboreal prosimian having foxy faces and long furry tails

bush baby (noun)	lemur (noun)
agile long-tailed nocturnal African lemur with dense woolly fur and large eyes and ears	large-eyed arboreal prosimian having foxy faces and long furry tails