rat terrier vs terrier

rat terrier and terrier both are nouns.

Word	Noun	Adjective	Verb	Adverb
rat terrier	Yes	No	No	No
terrier	Yes	No	No	No

As nouns, terrier is a hypernym of rat terrier; that is, terrier is a word with a broader meaning than rat terrier:

rat terrier: any of several breeds of terrier developed to catch rats
terrier: any of several usually small short-bodied breeds originally trained to hunt animals living underground

rat terrier (noun)	terrier (noun)
any of several breeds of terrier developed to catch rats	any of several usually small short-bodied breeds originally trained to hunt animals living underground