fire-eater vs grouch

fire-eater and grouch both are nouns.

Word	Noun	Adjective	Verb	Adverb
fire-eater	Yes	No	No	No
grouch	Yes	No	Yes	No

As nouns, grouch is a hypernym of fire-eater; that is, grouch is a word with a broader meaning than fire-eater:

Other hypernyms of fire-eater include churl, crank, crosspatch, grump.

fire-eater (noun)	grouch (noun)
a performer who pretends to swallow fire	a bad-tempered person
a belligerent grouch
a member of a fire department who tries to extinguish fires

fire-eater (verb)	grouch (verb)
	show one's unhappiness or critical attitude