watchdog vs attack dog

watchdog and attack dog both are nouns.

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

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

Other hyponyms of watchdog include kuvasz, housedog, schipperke, pinscher.

watchdog (noun)	attack dog (noun)
a dog trained to guard property	a watchdog trained to attack on command
a guardian or defender against theft or illegal practices or waste