butterfish vs rock gunnel

butterfish and rock gunnel both are nouns.

Word	Noun	Adjective	Verb	Adverb
butterfish	Yes	No	No	No
rock gunnel	Yes	No	No	No

As nouns, butterfish and rock gunnel are synonyms defined as:

butterfish and rock gunnel: slippery scaleless food fish of the northern Atlantic coastal waters

Other synonyms of butterfish include Pholis gunnellus.

butterfish (noun)	rock gunnel (noun)
small marine fish with a short compressed body and feeble spines	slippery scaleless food fish of the northern Atlantic coastal waters
slippery scaleless food fish of the northern Atlantic coastal waters
any of numerous small flat Atlantic food fish having smooth skin