an entrance that no one really knows about, an un recognised entrance
The cops came in the front so we cheesed it out the postern.
by Jon Provance December 03, 2006
1 more definition
a former employee made redundant by an organisation who is now doing work for free for that organisation, usually in the hope of being rehired when the economy improves.
She's trying to find a new direction, but in the mean time, she's effectively an IBM postern, still trying to direct sales leads towards her old employer.
by graviton August 25, 2010