let ‧ ter ‧ box /ˈletəbɒks $ ˈletərbɑːks/ BrE AmE noun [countable]
1 . British English a narrow hole in a door, or a special box outside a house where letters, packages etc are delivered SYN mail box American English
2 . British English a box in a post office or street, in which letters are posted SYN post box British English , mail box American English