set down vs plop

set down is not a noun while plop is a noun.

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

As verbs, plop is a hyponym of set down; that is, plop is a word with a more specific, narrower meaning than set down:

Other hyponyms of set down include flump, plank, plonk, plump, plump down, plunk, plunk down.

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

set down (verb)	plop (verb)
put down in writing; of texts, musical compositions, etc.	set (something or oneself) down with or as if with a noise
remove (cargo, people, etc.) from and leave	drop with the sound of something falling into water
put or settle into a position	drop something with a plopping sound
cause to sit or seat or be in a settled position or place
go ashore
reach or come to rest

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