What does "bulwark" mean?

Bulwark: That which secures against an enemy, or defends from attack; any means of defense or protection. The royal navy of England hath ever been its greatest defense, . . . the floating bulwark of our island. Blackstone.

Additional senses

  1. 2.pl. (Naut.) The sides of a ship above the upper deck.
  2. 3.To fortify with, or as with, a rampart or wall; to secure by fortification; to protect. Of some proud city, bulwarked round and armed With rising towers. Glover.

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