cutlass fish

from The American Heritage® Dictionary of the English Language, 4th Edition

• n. Any of several marine fishes of the genus Trichiurus, having a long, ribbonlike body and a pointed tail.

from the GNU version of the Collaborative International Dictionary of English

• n. a peculiar, long, thin, marine fish (Trichiurus lepturus) of the southern United States and West Indies, having a long whiplike scaleless body and sharp daggerlike teeth; -- called also frostfish, saber fish, silver eel, and, improperly, swordfish; also, several related members of the genus Trichiurus. It is closely related to snake mackerel.