put down vs plonk

put down is not a noun while plonk is a noun.

Word	Noun	Adjective	Verb	Adverb
put down	No	No	Yes	No
plonk	Yes	No	Yes	No

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

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

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

put down (verb)	plonk (verb)
put down in writing; of texts, musical compositions, etc.	set (something or oneself) down with or as if with a noise
make a record of; set down in permanent form
put in a horizontal position
remove (cargo, people, etc.) from and leave
cause to sit or seat or be in a settled position or place
put (an animal) to death
reduce in worth or character, usually verbally
cause to come to the ground