poison bush vs subshrub

poison bush and subshrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
poison bush	Yes	No	No	No
subshrub	Yes	No	No	No

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

poison bush: either of two Australian plants of the genus Swainsona that are poisonous to sheep
subshrub: low-growing woody shrub or perennial with woody base

Other hypernyms of poison bush include suffrutex.

poison bush (noun)	subshrub (noun)
either of two Australian plants of the genus Swainsona that are poisonous to sheep	low-growing woody shrub or perennial with woody base
any of various Australian evergreen shrubs of the genus Gastrolobium having whorled compound leaves poisonous to livestock and showy yellow to deep reddish-orange flowers followed by two-seeded pods