thunderhead vs cumulus cloud

thunderhead and cumulus cloud both are nouns.

Word	Noun	Adjective	Verb	Adverb
thunderhead	Yes	No	No	No
cumulus cloud	Yes	No	No	No

As nouns, cumulus cloud is a hypernym of thunderhead; that is, cumulus cloud is a word with a broader meaning than thunderhead:

thunderhead: a rounded projecting mass of a cumulus cloud with shining edges; often appears before a thunderstorm
cumulus cloud: a globular cloud

Other hypernyms of thunderhead include cumulus.

thunderhead (noun)	cumulus cloud (noun)
a rounded projecting mass of a cumulus cloud with shining edges; often appears before a thunderstorm	a globular cloud