terrier vs bullterrier

terrier and bullterrier both are nouns.

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

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

terrier: any of several usually small short-bodied breeds originally trained to hunt animals living underground
bullterrier: a powerful short-haired terrier originated in England by crossing the bulldog with terriers

terrier (noun)	bullterrier (noun)
any of several usually small short-bodied breeds originally trained to hunt animals living underground	a powerful short-haired terrier originated in England by crossing the bulldog with terriers