eavesdropper vs auditor

eavesdropper and auditor both are nouns.

Word	Noun	Adjective	Verb	Adverb
eavesdropper	Yes	No	No	No
auditor	Yes	No	No	No

As nouns, auditor is a hypernym of eavesdropper; that is, auditor is a word with a broader meaning than eavesdropper:

Other hypernyms of eavesdropper include attender, hearer, listener, snoop, snooper.

eavesdropper (noun)	auditor (noun)
a secret listener to private conversations	a qualified accountant who inspects the accounting records and practices of a business or other organization
	someone who listens attentively
	a student who attends a course but does not take it for credit