moonfish vs horse-head

moonfish and horse-head both are nouns.

Word	Noun	Adjective	Verb	Adverb
moonfish	Yes	No	No	No
horse-head	Yes	No	No	No

As nouns, moonfish and horse-head are synonyms defined as:

moonfish and horse-head: any of several silvery marine fishes with very flat bodies

Other synonyms of moonfish include Atlantic moonfish, dollarfish, horsefish, horsehead, Selene setapinnis.

moonfish (noun)	horse-head (noun)
large elliptical brightly colored deep-sea fish of Atlantic and Pacific and Mediterranean	any of several silvery marine fishes with very flat bodies
any of several silvery marine fishes with very flat bodies