plop vs come down

plop is a noun but come down is not a noun.

Word	Noun	Adjective	Verb	Adverb
plop	Yes	No	Yes	Yes
come down	No	No	Yes	No

As verbs, come down is a hypernym of plop; that is, come down is a word with a broader meaning than plop:

Other hypernyms of plop include descend, fall, go down.

plop (noun)	come down (noun)
the noise of a rounded object dropping into a liquid without a splash

plop (verb)	come down (verb)
set (something or oneself) down with or as if with a noise	get sick
drop with the sound of something falling into water	be the essential element
drop something with a plopping sound	criticize or reprimand harshly
	move downward and lower, but not necessarily all the way
	fall from clouds

plop (adverb)	come down (adverb)
with a short hollow thud