guard dog vs attack dog

guard dog and attack dog both are nouns.

Word	Noun	Adjective	Verb	Adverb
guard dog	Yes	No	No	No
attack dog	Yes	No	No	No

As nouns, attack dog is a hyponym of guard dog; that is, attack dog is a word with a more specific, narrower meaning than guard dog:

Other hyponyms of guard dog include kuvasz, housedog, schipperke, pinscher.

guard dog (noun)	attack dog (noun)
a dog trained to guard property	a watchdog trained to attack on command