Found 2 items, similar to mail slot.
English → English (WordNet) Definition: mail slot mail slot n : a slot (usually in a door) through which mail can be delivered
English → English (gcide) Definition: mail slot 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]