plonk vs flump

plonk is a noun but flump is not a noun.

Word	Noun	Adjective	Verb	Adverb
plonk	Yes	No	Yes	No
flump	No	No	Yes	No

As verbs, plonk and flump are synonyms defined as:

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

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

plonk (noun)	flump (noun)
the noise of something dropping (as into liquid)
a cheap wine of inferior quality

plonk (verb)	flump (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
	fall heavily