cow's head vs morel

cow's head and morel both are nouns.

Word	Noun	Adjective	Verb	Adverb
cow's head	Yes	No	No	No
morel	Yes	No	No	No

As nouns, morel is a hypernym of cow's head; that is, morel is a word with a broader meaning than cow's head:

cow's head: a morel with the ridged and pitted fertile portion attached to the stipe for about half its length
morel: any of various edible mushrooms of the genus Morchella having a brownish spongelike cap

cow's head (noun)	morel (noun)
a morel with the ridged and pitted fertile portion attached to the stipe for about half its length	any of various edible mushrooms of the genus Morchella having a brownish spongelike cap