plump down vs plunk down

plump down and plunk down both are verbs.

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

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

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

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

plump down (verb)	plunk down (verb)
set (something or oneself) down with or as if with a noise	set (something or oneself) down with or as if with a noise
drop heavily