1. a small gate or door, especially a private or secondary entrance to a castle, fort, or large building
Usage: historical

1. relating to or situated at the back or side; secondary
Usage: archaic

Examples

• The soldiers escaped through a hidden postern in the castle wall.
• She slipped out the postern gate to avoid the crowds at the main entrance.
• The medieval fortress had several postern doors for emergency exits.
• Guards were stationed at every postern to prevent unauthorized entry.
• The postern entrance was concealed behind thick ivy.
• They used the postern route to bring supplies into the besieged city.