An obstacle, barrier, or bulwark.
A barrier constructed across a road, especially as a military defence
A place of confrontation.
to close or block a road etc., using a barricade
to keep someone in (or out), using a blockade, especially ships in a port
A defensive wall or rampart.
A defense or safeguard.
A breakwater.
Any means of defence or security.
The planking or plating along the sides of a nautical vessel above her gunwale that reduces the likelihood of seas washing over the gunwales and people being washed overboard.
To fortify something with a wall or rampart.
To provide protection of defense for something.