overcrowd vs herd

overcrowd is not a noun while herd is a noun.

Word	Noun	Adjective	Verb	Adverb
overcrowd	No	No	Yes	No
herd	Yes	No	Yes	No

As verbs, herd is a hypernym of overcrowd; that is, herd is a word with a broader meaning than overcrowd:

Other hypernyms of overcrowd include crowd.

overcrowd (noun)	herd (noun)
	a group of cattle or sheep or other domestic mammals all of the same kind that are herded by humans
	a group of wild mammals of one species that remain together: antelope or elephants or seals or whales or zebra
	a crowd especially of ordinary or undistinguished persons or things

overcrowd (verb)	herd (verb)
crowd together too much	move together, like a herd
cause to crowd together too much	cause to herd, drive, or crowd together
	keep, move, or drive animals