harass vs nark

harass is not a noun while nark is a noun.

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

As verbs, nark is a hypernym of harass; that is, nark is a word with a broader meaning than harass:

Other hypernyms of harass include annoy, bother, chafe, devil, get at, get to, gravel, irritate, nettle, rag, rile, vex.

harass (noun)	nark (noun)
	an informer or spy working for the police
	a lawman concerned with narcotics violations

harass (verb)	nark (verb)
exhaust by attacking repeatedly	inform or spy (for the police)
annoy continually or chronically	cause annoyance in; disturb, especially by minor irritations