abert
n. C2 Proficiency US //ˈæbɝt// abert
n. a small, round hole in a wall or door that is used for looking through or letting in light. It is often used in old buildings or for security.
n. a small, round opening in a wall or door, typically used for observation or ventilation. Often associated with historical architecture or security features.
The guard looked through the small abert in the wall.
The old stone cottage had a narrow abert in the kitchen door to allow light in during the winter.
Architects of the medieval period often incorporated an abert into the design of a tower to provide a discreet means of observation without compromising the structural integrity of the outer wall.