chaparral broom vs shrub

chaparral broom and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
chaparral broom	Yes	No	No	No
shrub	Yes	No	No	No

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

chaparral broom: widely spreading evergreen shrub of southwestern United States with flower heads in a leafy panicle
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of chaparral broom include bush.

chaparral broom (noun)	shrub (noun)
widely spreading evergreen shrub of southwestern United States with flower heads in a leafy panicle	a low woody perennial plant usually having several major stems