I. ˈpōstə(r)n, ˈpäs- noun
( -s )
Etymology: Middle English posterne, from Old French, alteration of posterle, from Late Latin posterula little secret door, diminutive of postera back door, from feminine of Latin posterus coming after — more at posterior
1.
a. : a back door or gate : a private or side entrance or way
b. : an obscure or disreputable way of entrance or escape
2. : a subterraneous passage between the ditch and the interior of either the main works or outworks of a fortification
II. adjective
: situated at the back, rear, or side : private
the postern gate of the abbey
a postern door