croak vs pip out

croak is a noun but pip out is not a noun.

Word	Noun	Adjective	Verb	Adverb
croak	Yes	No	Yes	No
pip out	No	No	Yes	No

As verbs, pip out is a hyponym of croak; that is, pip out is a word with a more specific, narrower meaning than croak:

croak: pass from physical life and lose all bodily attributes and functions necessary to sustain life
pip out: be killed or die

Other hyponyms of croak include abort, asphyxiate, stifle, suffocate, buy it, drown, predecease, famish, starve, fall, succumb, yield.

croak (noun)	pip out (noun)
a harsh hoarse utterance (as of a frog)

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