nudnik vs gadfly

nudnik and gadfly both are nouns.

Word	Noun	Adjective	Verb	Adverb
nudnik	Yes	No	No	No
gadfly	Yes	No	No	No

As nouns, gadfly is a hypernym of nudnik; that is, gadfly is a word with a broader meaning than nudnik:

Other hypernyms of nudnik include bore, dullard, blighter, cuss, pest, pesterer.

nudnik (noun)	gadfly (noun)
(Yiddish) someone who is a boring pest	any of various large flies that annoy livestock
	a persistently annoying person