A small rear gate, especially one in a fort or castle.(noun)
Situated in the back or at the side.(adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "postern" in a sentence
"IV. ii.91 (101,4) [that spirit's possess'd with haste, That wounds the unresisting postern with these strokes] The line is irregular, and the _unresisting postern_ so strange an expression, that want of measure, and want of sense, might justly raise suspicion of an errour, yet none of the later editors seem to have supposed the place faulty, except sir Tho."
"If the Germans and their allies crossed the river above and below the city, enveloping it from three sides, their bridgeheads across the river would not only be vulnerable to flank attacks, but the city itself would become a staging area for attacks, what a German general in a previous war had called a postern gate, an opening in a fortification that enabled the defenders to sally forth and surprise the besiegers."
"Running down the path, vaulting the little gate leading into the shrubberies, and dashing down a back way almost dark with the thick laurel-bushes overhead, he soon reached what was known as the postern door."