originally coined from a series of real life shootings in the postal service, it now usually means that someone is about to go nuts or off the deep end. the reason for going postal is usually trivial. also, means person on psychiatric meds that is off their pills.
after finding her computer's wallpaper had been changed again, Jane went postal on her fellow workers.
by Foozi100 July 24, 2005
When someone gets uncontrollably angry, often to a point of violence, usually in a workplace
After finding out Mark had another hour added to his 4 hour mail delivery shift, He brought a gun into work the next day and was reportedly going postal on fellow workers and customers
by NickBaggss November 29, 2015
Basicly, "going postal" is pulling a uzi, assault rifle or most any other firearm out from under your jacket and going nuts. That is, wasting anyone and anything you see, and then probably yourself. A bit like going apeshit.
Jim had left another burning paper bag of crap on John's doorstep, so John retaliated by going postal on his ass.
by Johnny The Homicidal Maniac August 19, 2004
When somebody gets really pissed and acts out in violence. They might push someone's head through a wall.
Addison is going postal and she is about to throw a punch at Timmy.
by mcnuggetdestroyer January 3, 2018
When you can't afford buying something you really want, and pitch a fit.
Alicia's broke, so she's going postal again....
by Emmi-chan June 17, 2005
To lash out violently and at random, often in a blind rage. Term taken from the 1990's incidents of workplace violence involving US Postal System workers.
I was so angry at work with the new workload, I was afraid I'd go postal.
by Unidyne March 12, 2005
To exact calculated revenge on co-workers or schoolmates, usually with a firearm, after being fired or expelled or just feeling extremely hard-done-by.

Software tester Michael McDermott shot and killed seven co-workers in 2000 after having his pay docked to cover back taxes.
A disgruntled former worker went postal today leaving seven dead, including two accountants he had accused of being 'Nazis' the day before.
by bee March 22, 2005