Definition of go postal in US English:

go postal

phrase

US
informal
  • Become crazed and violent, especially as the result of stress.

    • ‘Against the odds, you will find the self-restraint and strength of character to restrain yourself from going postal at annoying chattery colleagues.’
    • ‘However, instead of going postal and risk the chance you may do something you'll regret later, take his/her picture and throw darts at it.’
    • ‘The talk was that someone went postal at the docks.’
    • ‘You're not the only one who's lost out before, but you don't see me going postal on a hospital room!’
    • ‘This was not some guy from the Midwest who'd gone postal on his co-workers.’
    • ‘I survived about thirty-five years of it myself without calling in sick or making colossal mistakes or going postal whenever it was that time of the month.’
    • ‘I guess there's no use in screaming for help since I doubt our friends have gone postal and are out to kill us.’
    • ‘I ask one question about her to my father and he goes postal on me.’
    • ‘I ran the department that particular festive season, and I felt like going postal pretty much every day in the stretch before Christmas, believe me.’
    • ‘It was intentional, a case of someone going postal.’