cherry plum vs plum tree

cherry plum and plum tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
cherry plum	Yes	No	No	No
plum tree	Yes	No	No	No

As nouns, plum tree is a hypernym of cherry plum; that is, plum tree is a word with a broader meaning than cherry plum:

cherry plum: small Asiatic tree bearing edible red or yellow fruit
plum tree: any of several trees producing edible oval fruit having a smooth skin and a single hard stone

Other hypernyms of cherry plum include plum.

cherry plum (noun)	plum tree (noun)
an edible fruit of the small tree Prunus cerasifera.	any of several trees producing edible oval fruit having a smooth skin and a single hard stone
small Asiatic tree bearing edible red or yellow fruit