Definitions for "Postern"
Keywords:  sally, castle, siege, sortie, ditch
Originally, a back door or gate; a private entrance; hence, any small door or gate.
A subterraneous passage communicating between the parade and the main ditch, or between the ditches and the interior of the outworks.
Secondary gate or door. (Gies, Joseph and Francis. Life in a Medieval Castle, 226) Small gateway, secondary to the main entrance. (Kenyon, John R. Medieval Fortifications, 211) Related terms: Castle / Sally-Port
Back; being behind; private.
A lesser, and private gateway.
In Christian architecture: A small gateway, sometimes concealed, at the back of a monastery.