Definition of "GPO"

GPO

proper noun
1. Initialism of General Post Office.
  Quotations
  "Yes. He gets to Paris at seven in the morning. He promised to telephone the first thing.""You expensive little monkey!""Why?""It's ten shillings for three minutes, or something like that, and you have to go to the G.P.O. or the Mansion House or some such place, I believe."
  1909, Algernon Blackwood, You May Telephone From Here
2. Initialism of German patent office.
3. (US) Initialism of Government Publishing Office, formerly Government Printing Office.
4. (Canada, politics) Initialism of Green Party of Ontario.
5. (Israel) Initialism of government press office.
noun
plural GPOs
1. (US) Initialism of group purchasing organization.