0 a small hole in a door or a wall through which you can look, especially without being seen -- （門或牆上的）窺視孔；貓眼
The two peepholes assert the viewer is looking with both eyes, making the optical experience similar to looking into the illusory space of a stereoscope.
They are narrow cells with little peepholes in the doors, and the inmates are required to slop them out each morning.
Some stores have one-way mirrors to spy for the light-fingered and sometimes to catch the careless; there are the peepholes through the doors.
Towers have limited access, contain few windows and many have narrow slots or peepholes placed in the walls.
