cumulus vs compost pile

cumulus and compost pile both are nouns.

Word	Noun	Adjective	Verb	Adverb
cumulus	Yes	Yes	No	No
compost pile	Yes	No	No	No

As nouns, compost pile is a hyponym of cumulus; that is, compost pile is a word with a more specific, narrower meaning than cumulus:

cumulus: a collection of objects laid on top of each other
compost pile: a heap of manure and vegetation and other organic residues that are decaying to become compost

cumulus (noun)	compost pile (noun)
a collection of objects laid on top of each other	a heap of manure and vegetation and other organic residues that are decaying to become compost
a globular cloud

cumulus (adjective)	compost pile (adjective)
of or related to cumulous clouds