Home › Words › M › mousefishmousefishmousefish · noun — the sargassum fish, Histrio histrio.Definition from Wiktionary (CC BY-SA 3.0).EtymologyFrom mouse + fish.nounThe sargassum fish, Histrio histrio.Gonorynchus gonorynchus, a kind of beaked salmon.Definitions & examples from Wiktionary (CC BY-SA 3.0).