1 [C] a place where you can buy stamps, send letters, etc:
Where's the main post office? * You can buy your stamps at the post office. * a post office counter
2 (the Post Office) [sing.] (abbreviation PO) the national organization in many countries that is responsible for collecting and delivering letters, etc:
He works for the Post Office.
3 [U] (AmE) = POSTMAN'SKNOCK
