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.
Origin of flap door
First recorded in 1835–45
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for flap door
Historical Examples of flap door
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
In the side of his wagon cover next to me was a flap-door, which, the day being fine, was fastened open.