grumbler vs complainer

grumbler and complainer both are nouns.

Word	Noun	Adjective	Verb	Adverb
grumbler	Yes	No	No	No
complainer	Yes	No	No	No

As nouns, grumbler and complainer are synonyms defined as:

grumbler and complainer: a person given to excessive complaints and crying and whining

Other synonyms of grumbler include bellyacher, crybaby, moaner, sniveller, squawker, whiner.

grumbler (noun)	complainer (noun)
a person given to excessive complaints and crying and whining	a person given to excessive complaints and crying and whining