malcontent vs caviller

malcontent and caviller both are nouns.

Word	Noun	Adjective	Verb	Adverb
malcontent	Yes	Yes	No	No
caviller	Yes	No	No	No

As nouns, caviller is a hyponym of malcontent; that is, caviller is a word with a more specific, narrower meaning than malcontent:

malcontent: a person who is discontented or disgusted
caviller: a disputant who quibbles; someone who raises annoying petty objections

Other hyponyms of malcontent include caviler, pettifogger, quibbler, sorehead, squabbler.

malcontent (noun)	caviller (noun)
a person who is discontented or disgusted	a disputant who quibbles; someone who raises annoying petty objections

malcontent (adjective)	caviller (adjective)
discontented as toward authority