noun
trapdoor; flap door
A door that opens by flipping upward, often hinged at the top or bottom; used for attic access, cellar entrances, or small service hatches.
屋根裏へ上がるには、天井の跳ね上げ戸を押し上げます。
To go up to the attic, push up the trapdoor in the ceiling.
床に跳ね上げ戸があって、地下室に降りられる。
There is a trapdoor in the floor that leads down to the basement.
Compound of 跳ね上げ (はねあげ, 'flipping up') + 戸 (ど, 'door'). The spelling 撥ね上げ戸 uses a variant kanji for the same verb.