bush hibiscus vs shrub

bush hibiscus and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
bush hibiscus	Yes	No	No	No
shrub	Yes	No	No	No

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

bush hibiscus: southern and western Australian shrub with unlobed or shallowly lobed toothed leaves and purple flowers; sometimes placed in genus Hibiscus
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of bush hibiscus include bush.

bush hibiscus (noun)	shrub (noun)
southern and western Australian shrub with unlobed or shallowly lobed toothed leaves and purple flowers; sometimes placed in genus Hibiscus	a low woody perennial plant usually having several major stems