plump vs plump out

plump is a noun but plump out is not a noun.

Word	Noun	Adjective	Verb	Adverb
plump	Yes	Yes	Yes	Yes
plump out	No	No	Yes	No

As verbs, plump and plump out are synonyms defined as:

Other synonyms of plump include fat, fatten, fatten out, fatten up, fill out, flesh out.

plump (noun)	plump out (noun)
the sound of a sudden heavy fall

plump (adjective)	plump out (adjective)
sufficiently fat so as to have a pleasing fullness of figure

plump (verb)	plump out (verb)
give support (to) or make a choice (of) one out of a group or number	make fat or plump
make fat or plump	depart suddenly
set (something or oneself) down with or as if with a noise
drop sharply

plump (adverb)	plump out (adverb)
straight down especially heavily or abruptly