Definition of jackknife clam in US English:

jackknife clam

noun

North American
  • A burrowing bivalve mollusk with a long, slender shell that resembles the handle of a straight razor.

    Family Solenidae: Ensis and other genera

    British term razor shell; also called razor clam
    • ‘Jackknife clams inhabit bays, estuaries, and lagoons near the mean low tide level in mud or muddy sand flats.’
    • ‘The razor clams served up at Wei Wei are also known as Atlantic Jackknife Clams, found along the Eastern Atlantic coasts ranging from South Carolina to Canada. The meat has the expected texture of clam, but a sweet flavor that may remind you of lobster.’