to keep someone in (or out), using a blockade, especially ships in a port
to close or block a road etc., using a barricade
A barrier constructed across a road, especially as a military defence
An obstacle, barrier, or bulwark.
A place of confrontation.
To keep safe; to defend; to guard; to prevent harm coming to.
To book a passenger on a later flight if there is a chance they will not be able to board their earlier reserved flight.