| Noun | 1. | Po - 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 Synonyms: atomic number 84, polonium |
| 2. | PO - a noncommissioned officer in the navy with a rank comparable to sergeant in the army Synonyms: P.O., petty officer | |
| 3. | Po - a European river; flows into the Adriatic Sea Synonyms: Po River | |
| 4. | PO - an independent agency of the federal government responsible for mail delivery (and sometimes telecommunications) between individuals and businesses in the United States |