harass vs dun

harass is not a noun while dun is a noun.

Word	Noun	Adjective	Verb	Adverb
harass	No	No	Yes	No
dun	Yes	Yes	Yes	No

As verbs, dun is a hyponym of harass; that is, dun is a word with a more specific, narrower meaning than harass:

Other hyponyms of harass include goad, needle, bedevil, crucify, frustrate, rag, torment, haze.

harass (noun)	dun (noun)
	horse of a dull brownish grey color
	a color or pigment varying around a light grey-brown color

harass (adjective)	dun (adjective)
	of a dull greyish brown to brownish grey color

harass (verb)	dun (verb)
exhaust by attacking repeatedly	make a dun color
annoy continually or chronically	cure by salting
	persistently ask for overdue payment
	treat cruelly