postern

Meanings

1. A back gate, back door, side entrance, or other gateway distinct from the main entrance, especially in a city wall or fortification.
2. A separate or hidden way in or out of a place, situation etc.
3. A subterranean passage communicating between the parade and the main ditch, or between the ditches and the interior of the outworks.

1. Situated at the rear; posterior.

Etymology

From Old French posterne, alteration of posterle, from Late Latin posterula (“back door”), from Latin posterus (“later”).