Definition of jackknife fish in US English:

jackknife fish

noun

  • A strikingly marked fish with a long upright dorsal fin, which lives among rocks and corals in the warm waters of the western Atlantic.

    "Equetus lanceolatus", family "Sciaenidae"

    • ‘The Jackknife fish will comb the sandy bottom looking for worms, crustaceans, and small fish if it is hungry. It may even eat the occasional fireworm.’
    • ‘The jackknife fish is a particularly handsome species, which immediately catches the eye with its long tapering first dorsal fin.’