Definition of: postern

(pōs′tərn, pos′-) noun
1. A back gate or door; a private entrance, especially a small gate beside a large one in a fortified place.
2. A covered passage closed by a gate and leading from a bastion to the ditch.
—adjective Situated at the back; private: a postern gate. [<OF posterne, posterle <L posterus. See POSTERIOR.]