Polonium

(Latin) per os
By mouth; orally

Abbreviation for Post Office.
1 petty officer
2 postal order
3 post office
4 purchase order

A European river; flows into the Adriatic Sea; Also called: Po River.
Longest river in Italy, flowing from the Cottian Alps to the Adriatic Sea; length 668 km/415 mi. Its valley is fertile and contains natural gas. The river is heavily polluted with nitrates, phosphates, and arsenic.