1. a small hole in a door or wall through which one can look secretly or safely

Examples

• She looked through the peephole to see who was at the door.
• The apartment door had a peephole for security purposes.
• He drilled a small peephole in the fence to watch the neighbors.
• The hotel room door featured a wide-angle peephole.
• Before opening the door, always check the peephole first.
• The peephole was too high for the child to reach.