a radioactive metallic element that is similar to tellurium and bismuth; occurs in uranium ores but can be produced by bombarding bismuth with neutrons in a nuclear reactor
同义词：polonium, atomic number 84
a noncommissioned officer in the navy with a rank comparable to sergeant in the army
同义词：petty officer, P.O.
a European river; flows into the Adriatic Sea
同义词：Po River
an independent agency of the federal government responsible for mail delivery (and sometimes telecommunications) between individuals and businesses in the United States
同义词：United States Post Office, US Post Office, Post Office
