crowd together vs swarm

crowd together is not a noun while swarm is a noun.

Word	Noun	Adjective	Verb	Adverb
crowd together	No	No	Yes	No
swarm	Yes	No	Yes	No

As verbs, swarm is a hyponym of crowd together; that is, swarm is a word with a more specific, narrower meaning than crowd together:

Other hyponyms of crowd together include mass, overcrowd, pour, pullulate, stream, teem, herd, jam, mob, pack, pile, throng.

crowd together (noun)	swarm (noun)
	a group of many things in the air or on the ground
	a moving crowd

crowd together (verb)	swarm (verb)
to gather together in large numbers	move in large numbers
	be teeming, be abuzz