bullhead vs bullhead catfish

bullhead and bullhead catfish both are nouns.

Word	Noun	Adjective	Verb	Adverb
bullhead	Yes	No	No	No
bullhead catfish	Yes	No	No	No

As nouns, bullhead and bullhead catfish are synonyms defined as:

bullhead and bullhead catfish: any of several common freshwater catfishes of the United States

bullhead (noun)	bullhead catfish (noun)
freshwater sculpin with a large flattened bony-plated head with hornlike spines	any of several common freshwater catfishes of the United States
any of several common freshwater catfishes of the United States