any of a family (Hemirhamphidae, order Atheriniformes) of small, long-bodied, tropical marine bony fishes with a greatly extended lower jaw and a short upper jaw
See halfbeak in American Heritage Dictionary 4
(hăfˈbēkˌ, häfˈ-)
noun
Any of various slender, bony, live-bearing tropical freshwater fishes of the family Hemiramphidae, characterized by a silvery appearance and an elongated lower jaw.