·noun The anterior segment of the shell of trilobites.
II. Buckler ·vt To Shield; to Defend.
III. Buckler ·noun One of the large, bony, external plates found on many ganoid fishes.
IV. Buckler ·noun A kind of shield, of various shapes and sizes, worn on one of the arms (usually the left) for protecting the front of the body.
V. Buckler ·noun A block of wood or plate of iron made to fit a hawse hole, or the circular opening in a half-port, to prevent water from entering when the vessel pitches.