plunk down vs plunk

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

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

As verbs, plunk down and plunk are synonyms defined as:

plunk down and plunk: set (something or oneself) down with or as if with a noise

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

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

plunk down (verb)	plunk (verb)
set (something or oneself) down with or as if with a noise	pull lightly but sharply with a plucking motion
	set (something or oneself) down with or as if with a noise
	drop steeply
	make or move along with a sound as of a horse's hooves striking the ground

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