Po

(noun) 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: polonium, atomic number 84.

(noun) a noncommissioned officer in the Navy or Coast Guard with a rank comparable to sergeant in the Army. Synonyms: petty officer, PO, P.O..

(noun) a European river; flows into the Adriatic Sea. Synonyms: Po River.

(noun) an independent agency of the federal government responsible for mail delivery (and sometimes telecommunications) between individuals and businesses in the United States. Synonyms: United States Post Office, US Post Office, Post Office, PO.