Also called falling door. a door hinged at the bottom so as to fall downward and outward.
a door placed horizontally or on a shallow incline, as an exterior cellar door.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use flap door in a sentence
At the front is a flap door which is kept closed while the torpedo is slipped into its place.The Romance of War Inventions | Thomas W. Corbin
In the side of his wagon cover next to me was a flap-door, which, the day being fine, was fastened open.
In front of each tier of 12 compartments is a flap door opening downward.Handwork in Wood | William Noyes
The other part of the shop is closed by a flap-door that does not show on the picture.Topsy-Turvy Land | Samuel M. Zwemer