(OFFICE) [noun] [C or U] - abbreviation for post office, see at post (LETTERS)A PO Box is a numbered box in a post office to which someone's letters and parcels can be sent and from which the person can collect them.Write to P.O. Box 123.
PO
Meaning of PO in English
Cambridge English vocab. Кембриджский английский словарь. 2012