buy the farm vs croak

buy the farm is not a noun while croak is a noun.

Word	Noun	Adjective	Verb	Adverb
buy the farm	No	No	Yes	No
croak	Yes	No	Yes	No

As verbs, buy the farm and croak are synonyms defined as:

buy the farm and croak: pass from physical life and lose all bodily attributes and functions necessary to sustain life

buy the farm (noun)	croak (noun)
	a harsh hoarse utterance (as of a frog)

buy the farm (verb)	croak (verb)
pass from physical life and lose all bodily attributes and functions necessary to sustain life	pass from physical life and lose all bodily attributes and functions necessary to sustain life
	make complaining remarks or noises under one's breath
	utter a hoarse sound, like a raven