Definition of mousefish in US English:

mousefish

noun

  • 1The sargassum fish, Histrio histrio.

  • 2A slim, brightly coloured Indo-Pacific fish, Gonorhynchus gonorhynchus (family Gonorhynchidae), which burrows in sand on the seabed; also called beaked salmon, rat-fish.

Origin

Early 19th century.