pesterer vs gadfly

pesterer and gadfly both are nouns.

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

As nouns, pesterer and gadfly are synonyms defined as:

Other synonyms of pesterer include blighter, cuss, pest.

pesterer (noun)	gadfly (noun)
a persistently annoying person	any of various large flies that annoy livestock
	a persistently annoying person