noun the anterior segment of the shell of trilobites.
2. buckler ·vt to shield; to defend.
3. buckler ·noun one of the large, bony, external plates found on many ganoid fishes.
4. 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.
5. 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.