set down vs plunk

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

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

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

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

set down (noun)	plunk (noun)
	(baseball) hitting a baseball so that it drops suddenly
	a hollow twanging sound

set down (verb)	plunk (verb)
put down in writing; of texts, musical compositions, etc.	pull lightly but sharply with a plucking motion
remove (cargo, people, etc.) from and leave	set (something or oneself) down with or as if with a noise
put or settle into a position	drop steeply
cause to sit or seat or be in a settled position or place	make or move along with a sound as of a horse's hooves striking the ground
go ashore
reach or come to rest

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