Irish gorse vs shrub

Irish gorse and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
Irish gorse	Yes	No	No	No
shrub	Yes	No	No	No

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

Irish gorse: very spiny and dense evergreen shrub with fragrant golden-yellow flowers; common throughout western Europe
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of Irish gorse include bush.

Irish gorse (noun)	shrub (noun)
very spiny and dense evergreen shrub with fragrant golden-yellow flowers; common throughout western Europe	a low woody perennial plant usually having several major stems