pit bull terrier vs bullterrier

pit bull terrier and bullterrier both are nouns.

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

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

pit bull terrier: American breed of muscular terriers with a short close-lying stiff coat
bullterrier: a powerful short-haired terrier originated in England by crossing the bulldog with terriers

Other hypernyms of pit bull terrier include bull terrier.

pit bull terrier (noun)	bullterrier (noun)
American breed of muscular terriers with a short close-lying stiff coat	a powerful short-haired terrier originated in England by crossing the bulldog with terriers