cluster vs agglomerate

cluster and agglomerate both are nouns.

Word	Noun	Adjective	Verb	Adverb
cluster	Yes	No	Yes	No
agglomerate	Yes	Yes	Yes	No

As verbs, agglomerate is a hyponym of cluster; that is, agglomerate is a word with a more specific, narrower meaning than cluster:

cluster (noun)	agglomerate (noun)
a grouping of a number of similar things	a collection of objects laid on top of each other
	volcanic rock consisting of large fragments fused together

cluster (adjective)	agglomerate (adjective)
	clustered together but not coherent

cluster (verb)	agglomerate (verb)
gather or cause to gather into a cluster	form into one cluster
come together as in a cluster or flock