attacker vs harrier

attacker and harrier both are nouns.

Word	Noun	Adjective	Verb	Adverb
attacker	Yes	No	No	No
harrier	Yes	No	No	No

As nouns, harrier is a hyponym of attacker; that is, harrier is a word with a more specific, narrower meaning than attacker:

attacker (noun)	harrier (noun)
someone who attacks	hawks that hunt over meadows and marshes and prey on small terrestrial animals
	a hound that resembles a foxhound but is smaller; used to hunt rabbits
	a persistent attacker