/moohn"fish'/ , n. , pl. ( esp. collectively ) moonfish , ( esp. referring to two or more kinds or species ) moonfishes .
1. Also called horsefish, horsehead . any of several silvery marine fishes of the genus Selene, having a very compressed body and inhabiting shallow coastal waters.
2. the opah.
3. any of various other rounded, silvery fishes.
[ 1640-50; MOON + FISH ]