noun
door peephole; door viewer
A small lens fitted into a door to see who is outside. Wasei-eigo from 'door eye'; the English equivalent is 'peephole' or 'door viewer'. Often called ドアスコープ as well.
wasei-eigo (Japanese-coined English), from door eye
See also: ドアスコープ
ドアアイから外を見ると、知らない人が立っていた。
When I looked outside through the door peephole, a stranger was standing there.
このマンションのドアにはドアアイが付いていない。
The door of this apartment doesn't have a peephole.