2. (noun)polonium, Po, atomic number 84 a radioactive metallicelement that is similar to tellurium and bismuth; occurs in uranium ores but can be produced by bombarding bismuth with neutrons in a nuclear reactor
3. (noun)Po, Po River a European river; flows into the Adriatic Sea
4. (noun)United States Post Office, US Post Office, Post Office, PO an independentagency of the federalgovernment responsible for maildelivery (and sometimes telecommunications) between individuals and businesses in the United States