Dictionary:

postern

  (pō'stərn, pŏs'tərn)

A small rear gate, especially one in a fort or castle.

Situated in the back or at the side.

[Middle English posterne, from Old French, alteration of posterle, from Late Latin posterula, diminutive of Latin posterus, behind. See posterior.]

adjective

Located in the rear: back, hind, hindmost, posterior, rear¹. Nautical after. See precede/follow.

1. A minor, often inconspicuous, entry.
2. A small door near a larger one.
3. Any small door or gate, esp. one far from the main gate in a fortified place.
4. Same as sally port.

postern, 2

Postern, Manila. Tomás Sanz. 1783. SHM

South-eastern postern, Puilaurens castle

A postern is a secondary door or gate, particularly in a fortification such as a city wall or castle curtain wall. Posterns were often located in a concealed location, allowing the occupants to come and go inconspicuously. In the event of a siege, a postern could act as a sally port, allowing defenders to make a sortie on the besiegers.

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