debtor vs defaulter

debtor and defaulter both are nouns.

Word	Noun	Adjective	Verb	Adverb
debtor	Yes	No	No	No
defaulter	Yes	No	No	No

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

debtor: a person who owes a creditor; someone who has the obligation of paying a debt
defaulter: someone who fails to meet a financial obligation

Other hyponyms of debtor include deadbeat, fly-by-night, mortgager, mortgagor.

debtor (noun)	defaulter (noun)
a person who owes a creditor; someone who has the obligation of paying a debt	a contestant who forfeits a match
	someone who fails to meet a financial obligation
	someone who fails to make a required appearance in court