flap door

noun

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. 2018

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.
In the Early Days along the Overland Trail in Nebraska Territory, in 1852
Gilbert L. Cole