PO Box BrE AmE British English , P.O. Box American English /ˈpiː əʊ bɒks $ -oʊ bɑːks/ noun [countable]
(post office box) used before a number as an address at a post office where letters to you can be sent:
Write to P.O. Box 714, Key Largo, Florida.
PO BOX
Meaning of PO BOX in English
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012