'mail slot' definitions:
Definition of 'mail slot'
From: WordNet
noun
A slot (usually in a door) through which mail can be delivered
Definition of 'mail slot'
From: GCIDE
- mail slot \mail slot\ n. A usually horizontal slot in a door through which mail can be delivered. It often has a hinged cover to keep the opening cloised when not in use. [WordNet 1.5 +PJC]